When we met last week, to toast the occasion with a pre-birthday drink, Kinnear was quick to put the landmark into perspective. "I'm pleased, thankful, to get there and be in good health. A lot of people don't. I lost my sister when she was 32. She died of cancer at a very young age. I lost a friend in Cyril Knowles who died very young." He also lost his natural father, and stepfather, when he was barely in his teens.
"You do take stock," Kinnear said. "Everyone wants to get their half- century done, bat and pads on, 50 not out. But it is on you before you know it. Age seems to pass you by at times, you are working so hard. Sometimes you think, `I could probably have enjoyed myself more when I was younger', but you don't know it at the time.
"I look back at my first Cup final. I was 20 years of age, playing for Spurs [against Chelsea in the 1967 FA Cup final]. It's just a vague memory. I can more or less remember walking out of the tunnel and looking round at 100,000 people. Then I was just concentrating on the game. I remember walking up for my medal, then the euphoria after the match, jogging round with the trophy, then it's gone. The big blow was missing the next day - the trip round on the open-top bus - as I had gone off to play for Ireland.
"I look back and I've had 35 years in the game, amazing really. At 15 years of age I went to Tottenham's youth team, I had 12 years there as a professional, and two more at Brighton. Then an achilles injury finished me. There's been a lot of changes, I've seen a lot of good things and bad things."
Things are looking good for Kinnear at the moment. Wimbledon are high in the Premiership and Kinnear is in demand. "A big club [Blackburn or Manchester City] came in for me two weeks ago. It would have made me financially secure. I turned it down. I have a great relationship with Sam [Hamman]. We have worked hard to be where we are. I have always thought we were a good enough team to win something. I believe in my players, we have beaten the best.
"It's hard, I don't have the strength in depth. Without the Sky money Dean Holdsworth would have gone well before now. I've been able to add to the squad instead. But if I lose Oyvind Leonhardsen I don't have an experienced player to replace him. Clubs like Newcastle and Manchester United can go out and buy someone. But if we stay injury-free we have a realistic chance of winning something."
It has been worse. "You should have seen what Doncaster was like when I was manager there. It was like a pub side - the chairman was even a publican. The biggest problem was finding the wages. He would come in and say: `I can't pay you this week because we are playing away from home - we've got no gate money.'
"The players would say: `The cheque's ain't gone in, gaffer. When are we going to get paid?' I'd say: `We're lucky. We've got a home game Saturday - you'll be paid Sunday.'
"At the end of the season the chairman said to me: `You've done a magnificent job keeping us up. I'd like to extend your contract.' I said: `I've got a year to go. Let's talk about it next season.'
"When I came back from holiday there were two faces I didn't recognise. They said: `We're with the new consortium. Your chairman sold out. And by the way, Billy Bremner's the new manager.' When I'd left for my holiday he was the manager of Leeds, but had since been sacked.
"I was on pounds 25,000 a year - they gave me pounds 12,000. Ray Harford is supposed to have come out of Blackburn with a quarter of a million. Times have changed and it shows the difference in clubs. When I left the secretary came running out and said to me: `We want the car back.' I said: `I've got to get home first. You'll have to come back down to London and pick it up.'
"I was out of work for two weeks, then Bobby Gould rang me up and made me reserve team manager here. I met Sam. That was seven years ago. I've been here ever since."
The rest is mystery. How do Wimbledon do it? Preparation, organisation and hard work would appear to be the key. Over a small cider [he was driving], Kinnear let slip a few illustrations of why he spends hours watching matches and making notes.
"I was so pleased the other week. We went to Sunderland and I said to them we have to worry about Ball. They said `Kevin Ball?' I said `Yes. To me he epitomises Sunderland. Work rate, blood and thunder, wants another scar on his face. He's very dangerous arriving in the box - if the right cross comes in he's not afraid to throw his head in.' I said to Vinnie [Jones], you pick him up, let Robbie [Earle] and Leo [Leonhardsen] bomb on. He and Vinne had a right ding-dong throughout the game, but it worked. I saw Chelsea against them the following week. Sunderland get it down the left wing and cross it - and who's diving in with his header, a clear header unmarked? Kevin Ball. Bang. Goal. Terry Burton [Wimbledon coach] comes in the following day and says to me: `See that goal, he had acres of room.'
"Before we played Sheffield Wednesday I said this goalkeeper [Kevin Pressman] mucks about with it - close him down quick. Efan [Ekoku] did, took the ball off him and put it in the net. Great start.
"A lot of goalkeepers start attacks. Peter Schmeichel is one so, when he catches it, one of our forwards goes in and stands on him, blocks him. He starts moaning to the ref, the crowd start booing, but by then we're back on our tails and have picked everybody up. He ends up kicking it, it's a 50-50 knock-down... and we work hard on that.
"You want to cut off the supply first. Against Blackburn I said to the full-backs: `If you do nothing else but press up on Gallacher and Wilcox, mark them tight and not allow them a cross, you have done a wonderful job for us. Because that will cut all the service to Sutton, who's by himself.'
"So, Wilcox gets the ball, Cunningham gets close, Wilcox gives it back to Le Saux. The midfield get close to their midfield, he's no option but to whack it to Sutton. One centre-half will challenge him, the other will drop off and pick it up. Sutton's standing there with his arms out all frustrated and we've got the ball. We did a professional job on them. They had a lot of ball but never hurt us."
The same applied to Villa in the Coca-Cola Cup but, at Villa Park on Sunday, Cunningham made the sort of mistake that defeats every coach's planning. When the centre pair followed up with another error Wimbledon were drawn out of defence and well beaten. The long unbeaten run was over.
However, the prospects remain good. Most of the squad are signed until the next century, crowds have risen - above Southampton and landlords Crystal Palace - and the club remains solvent. "We've never been in the red, Sam's very proud of that." The only irritant is Merton Council's failure to support a move back to the borough.
Kinnear has had more helpful political rulers - like the Prince of Nepal, where Kinnear coached the national side. He lent Kinnear his private plane and a pilot to fly along the Annapurna Mountains. "It's a prop job," Kinnear recalled. "We are flying on our side along the mountains about 20 feet from Everest. It's a real change of pants job. I look at Bonnie [his wife] and her knuckles are white. Some experience."
Kinnear made the most of his travels. He went elephant trekking while coaching in India, rode camels in Dubai and survived a riot in Malaysia. "The bricks were landing around the dug-out then they started on the players. We headed for the dressing room."
Eventually he came back with Dave Mackay to Doncaster. Now, after five years at Wimbledon, he is the second longest serving manager in the Premiership. "My ambition is to be here longer than Alex [Ferguson]," he laughs. "When he decides to retire they can give me a call."
One can imagine him leaving for Old Trafford, but not for many other jobs. He has rejected the lure of Ireland and a fat bank balance. Wimbledon has a place in his heart that could be matched only by Tottenham. In the meantime he is looking through a crowded holiday programme to the Coca- Cola Cup quarter-final at Bolton on 8 January. "That's the important one." Wembley, Europe, and silverware beckon.