It is all a matter of timing. A Cup final in August, as opposed to May as before, means that the winners have to get their feet back on the ground very quickly.
So far, Hull have failed to do so. In their three games since their unforgettable triumph at Cardiff they have scraped just one win - an uninspired run which has seen them slip down to fifth place in the table, which means that they face a play-off exit if they cannot win at Warrington on Saturday.
Hull's supporters have put it into words. "It doesn't matter what we do for the rest of the season," they say. "We've got what we want." Sometimes it has looked as though the players agreed with them.
"We've been suffering from a bit of a hangover," says Swain. In fact, Hull celebrated in a style that did not quite match England's cricketers but which still squeezed every last drop of euphoria from their first Challenge Cup for 23 years and their first trophy for 14 - Ashes-length waits the pair of them.
"I think it's going to be hard for any team that wins the Challenge Cup now to get their attitude right in time for the play-offs. We've struggled a bit with that."
All the same, the New Zealand Test hooker, who is credited with bringing a new depth of professionalism to Hull, thought he detected a turning of the tide in the defeat by Warrington in the last match of the regular season last Friday.
"We've not quite been right. Everyone has noticed it, but, after we let in 16 easy points in the first 20 minutes last weekend, I thought our forwards woke up for the first time since Cardiff.
"Jamie Thackray and Paul King came on and we had a real go at them."
It was not enough to turn the game around and their 30-16 defeat means that they must face Warrington - and Andrew Johns - again at the Halliwell Jones Stadium this weekend.
In theory, Johns should carry less mystique this time after a relatively subdued display at the KC Stadium.
"We know what to expect," Swain says. "He was quite quiet, but having said that he had a hand in three tries. We still don't expect him to be as quiet this week.
"We didn't make any special plans for him. For 10 years in the NRL in Australia, coaches have tried to come up with a plan to keep him quiet and they haven't managed it.
"You just have to try to look after his runners and not concentrate too much on him, or you give people like Lee Briers too much room."
Swain twice gave Briers some extra help by throwing intercepted passes - a navigational error he will not want to repeat at Warrington.
As an Australian-born and -based Kiwi, Swain has plenty of experience of playing against Johns for the Melbourne Storm, with whom he won a Grand Final to place alongside this year's Challenge Cup.
After being a burden for the last three weeks, he now believes that Hull's Cup success will become an asset once more.
Like other Hull players, Swain has acknowledged that the squad stepped up its efforts under the coaching of the Cup specialist, John Kear, in the week before Cup ties; now they must do that for a sudden-death play-off.
"We're back in a knock-out situation," he says. "We've got to take the intensity we produced against St Helens in the semi-final and against Leeds in the final and bring it into the Super League competition. That's what we need to do, but it's all a matter of having the right attitude."
Swain's own form this season has been good enough to tempt him out of international retirement to play for New Zealand in the Tri-Nations. However, a lingering injury has now forced a re-think.
"I've got to tell them I won't be able to play," he says. "I need an operation to clean out my shoulder."
So Swain's season will end when Hull's does. After the heroics at the Millennium Stadium less than four weeks ago, he does not want it to end in anticlimax.
Super League draws record crowds
All but one club has increased its average attendance in Super League's best season yet for crowds, writes Dave Hadfield. Gates are up by four per cent to an average of 8,887 - the best not only since the start of Super League a decade ago, but also since the switch to two divisions in 1973.
Leeds were the best supported club during the regular season, which ended last weekend. Bradford are the only club to have shown a decrease in their attendances, but they still average 13,366.
The league leaders, St Helens, are the best represented club in the engage Super League Dream Team, selected on the basis of performances throughout the season, with five players voted in.
Paul Wellens, Jamie Lyon, Darren Albert, Keiron Cunningham and Paul Anderson are all in the notional line-up. Leeds are next best with four players named, two from Hull and one each from Warrington and Bradford. Ten of the players selected are British.
The sole Bradford player, the Great Britain captain Jamie Peacock, welcomed that level of representation. "It's a good sign for the British game," he said.
Warrington have Michael Wainwright and Ben Westwood fit for their play-off against Hull on Saturday after missing the end of the regular season with injuries.
"It's a question of who to leave out," said the Wolves coach, Paul Cullen, who will name both in his 20-man squad today.
The Huddersfield full-back, Paul Reilly, has withdrawn from England's European Nations Cup squad in order to have a rest.
Ben Roarty is in discussions with two Super League clubs after being released by Huddersfield because of a neck injury.
The London and former England prop, Francis Stephenson, is looking for a new club because he wants to return to his native Yorkshire.
Doncaster, known in recent years as the Dragons, have changed their name to the Lakers. The club, who were knocked out of the National League 1 play-offs on Sunday, have signed a 25-year lease to play at the new, 15,000-capacity Lakeside Sports Complex in the town.
Doncaster were the one promotion candidates to announce that they did not want to be promoted to Super League, but say that they intend to get there by 2009, either by promotion or as a franchise.
The South Sydney coach, Shaun McRae - previously in charge at St Helens and Hull - has come out in support of the attempt by the Oscar-winning actor, Russell Crowe, to buy the club.
Crowe is a long-standing supporter of the club, which avoided the wooden spoon for the first time since its readmission to the NRL in McRae's first season in charge.