It may not be the first thing that springs to mind when you philosophise the key to a happy marriage, but relationship researchers and therapists have declared that an annual 'performance review' - just like the one you probably dread at work - could be the key to lifelong love.

Those who have studied in depth what keeps couples together recommend that husbands, wives and romantic partners complete periodic assessments of how well their relationship is working, rather than waiting until it's too late to seek help.

Many typically leave it too long to go to therapy, they say, when they could recognise what is - and what isn't - working earlier, and thereby give themselves the greatest chance of success.

You don’t want to kitchen-sink the thing

&#13; <p>James Cordova, professor of psychology and director of the Center for Couples and Family Research at Clark University in Massachusetts</p>&#13;

And they recommend reviewing the state of your partnership together, and identifying goals for improvement, before problems become "unsolveable".

James Cordova, professor of psychology and director of the Center for Couples and Family Research at Clark University in Massachusetts, told the Wall Street Journal that it's the relationship equivalent of a "six-month dental checkup".

Dr Cordova also said that in a study he conducted in 2014, which was published in the Journal of Consulting and Clinical Psychology, 216 married couples were given questionnaires to assess the biggest strengths and weaknesses in their relationship.

Half of those who took part saw a therapist to go over their evaluations and form a plan to tackle their concerns, while the other half were told they were on a waiting list. After one and two years, those who had performed the checkup saw significant improvements in their relationship satisfaction, intimacy and feelings of acceptance - and fewer depressive symptoms. The couples who had the most problems in their marriage before the checkup saw the most improvement.

Dr Cordova also told the WSJ that while men often resist marriage therapy, they tend to appreciate marriage reviews, because they focus on a couple’s strengths and goals, as well as solving problems without blame. He said that when reviewing a relationship, you should always begin by identifying your strengths as a couple, then move on to discussing your concern s— but limit yourself to one or two. You don’t need to come up with a solution right away. Your primary aim should be to understand your partner and to be understood in return. “You don’t want to kitchen-sink the thing,” Dr Cordova said.

But, he warns, if the review makes your relationship worse, you may need counselling. “If you are doing it well, you can tell because you will feel closer to each other and will each feel understood," Dr Cordova said.