Last week Tony Blair finally got round to naming his retirement date, writes Lucy Kellaway

Last week I finally got round to opening an envelope that has been sitting on the hall table for ages that names my retirement date. Blair's is on June 27th, 2007. Mine turns out to be almost exactly 14 years to the day after Blair's. I retire on June 26th, 2021, which is my 62nd birthday.

Like Blair, but unlike most UK workers, I am on a final salary pension scheme. This means that the sum of money mentioned in my pension document is encouragingly large.

Alas, the day I start to draw it is discouragingly distant, so I can't help but look at Blair with some envy.

That isn't to say that I don't like my job. It is simply that when you're told you can stop working and be paid for it in 2021, it is human nature to want to do so sooner, preferably right now.

Next month Blair will be free to do as he likes. That is, he will be as free as it's possible to be if you have just bought a ludicrously expensive house.

Mortgage payments permitting, he'll be able to watch daytime television, do DIY, save the world, go on lecture tours or take other proper jobs. Such choice seems pretty nice.

I'm not alone in thinking that early retirement appeals. According to a survey released by Norwich Union last week, half of the British workforce would like to retire from their full-time jobs by 45 and do something more compassionate.

The survey seemed to think such mass altruism was good news, though if true it would be an economic calamity. Either way, it is academic, since half the population won't start working part-time for charities at 45 because they won't be able to afford it.

Still, there is a wealthy minority who can afford to retire in their 40s and early 50s and increasingly they are doing so. The lives of these people fascinate me: are they happier than they were before?

This must depend a bit on how horrid the old job was. Blair is quitting one of the most wretched jobs in the world, one that has made him age 20 years in just 10, so surely happiness beckons.

But that is to make the elementary mistake that Blair is like me, which clearly he isn't. Indeed, happiness after retirement mainly depends on personality, and as far as I can work out, people are divided into three different types.

There is the Warren Buffett type. These people live to work - money has nothing to do with it. Retirement for them is a disaster.

The next type is the Bill Gates type. This type works like a maniac in business and switches at middle age to work like a maniac to save the world. This type is getting more common, though you generally need a fortune to be effective at it.

Third are the couch potatoes, who simply prefer leisure to work. They reason that as work is relatively beastly, one should stop as soon as one has the money.

This type is rather frowned on, though I suspect they may be the most loveable of the lot.

Most of us have a mixture of Buffett, Gates and potato. The trouble is that it is very hard to know which parts dominate until you put it to the test, and then it can be too late.

I know all sorts of people who have taken early retirement because they hated their jobs, only to find they hated loafing around even more. Their potato side turned out to be underdeveloped.

Equally I can think of a few for whom the reverse was true. One very good friend left a well-paid job in the City a year ago, and I feared for him.

He seemed a classic alpha male almost certain to fall into severe depression without the prop of his job.

I saw him the other day and he told me he had just made a lamp and a lampshade. I have never seen him as triumphant.

It is of course hard to judge the happiness of others. People who have retired early almost always claim to be deliriously happy when asked by those who are still in work.

Recently I had lunch with a man who sold his company in his early 40s and made a small fortune.

He told me how happy he was, how he spends time with his wife and children, advises a few small businesses, and otherwise runs marathons.

This sounds like bliss apart from the last bit. Marathon runners always make me suspicious - it seems a sign of someone who is driven, but has nothing worthwhile to drive at.

I am also keeping my eye on those acquaintances who could stop work, but don't. I have a wealthy lawyer friend who has loathed her job for a decade.

She has easily enough money to quit but she goes on working.

The reason, I think, is that she can't decide if she is Buffett or potato, and doesn't dare take the risk. So she slogs on miserably.

By comparison, I am in a happier position: I slog on because I have to.

Lack of choice can be a very fine thing. And while I'm not taking decisions about my own future I'll be watching Blair's with interest.

My prediction: there isn't much potato in there.