Dom Joly: It's being 32 for years that's kept me on the telly

This will be the last column I write as a thirtysomething... ever. I can't believe that I'm going to "turn" 40 this week. I've been 32 for so long now that I've just got used to it. You can't really be over 32 and work in television unless you're a national treasure like Michael Palin, Jeremy Clarkson or Michael Winner... sorry, Winner isn't a national treasure, he's a national joke and he doesn't really do telly anyway apart from those toe-curling ads. But you know what I mean.

Apart from never being able to work on Channel 4 again, I'm pretty cool with the arrival of the big 40. After all, I was a Goth in my teens, an unemployed bum in my twenties and a man famous for dressing as a squirrel in my thirties – how bad can my forties be?

There are warning signs. I've taken up golf, started making weird "old man" noises when I get up from sitting down and I plucked three grey chest hairs this very morning. I am, however, still on my first marriage, haven't actually lost any hair yet and I'm fit enough not to need a stair lift – so things aren't all bad.

Someone really annoying told me that when you turned 40 you had to take a really hard look at your life and if you hadn't got your act together, now was the time. When you get to 50, he said, if you still hadn't got your act together it's too late. So I've started writing a sort of five-year plan.

Personally I'm determined to get my act together. First I want loads of money by the time I'm 50. It's not that I think money will automatically make me happy but, in the words of Woody Allen, "Money is better than poverty, if only for financial reasons".

I'm going to make this huge amount of money by either moving to the States and working in television over there, making some more Trigger Happy TVs over here or selling those photos I've got of Princess Diana snogging Ant and Dec in a hot tub. I need to think about the options, so I'll let you know what I decide.

I guess I officially become middle-aged this Thursday, so I'm also due a midlife crisis. This normally involves dressing like a teenager. (I already do this. Parents at my kids' school regularly ask Stacey whether she's married to the man with his trousers below his pants. And I sometimes feel like a paedophile when shopping in Carhartt and have started to shop online as it's less embarrassing.)

A midlife crisis also tends to involve the purchase of a flashy sports car, but I've already been through this embarrassing period when I briefly owned a Porsche. For six months I drove around feeling like a penis, getting nods at traffic lights from the sort of people I really hate. The last option is to have an affair with a young dolly bird.

Now it's true that Liz Hurley has been particularly forward these past two weeks – I saw her shopping in Cirencester, tried to avoid her, but she followed me for half an hour until I managed to lose her at the seafood counter in Waitrose. Anyway, she's an older woman – I'd need to choose some young local filly like... Kate Winslet – Jesus, I think I'd better stay happily married.

I don't actually mind getting old at all... honest. It's just the comfy middle-aged part that worries me. When I get properly old, I'll love it – I can urinate at bus stops, refuse to pay for anything, and shout random abuse at strangers to whom I take a mild dislike.

You just can't do that sort of thing at 40, sadly. There's still too much at stake.

I'm joking – I've got quite a good feeling about my next 10 years, everything's going to be fine... it's only the halfway point of my life with no going back, time's winged chariot, the inexorable approach of death... maybe I'm not as OK as I thought. All I want is to be able to do exactly what I want.

That's not asking too much, is it? After all, middle age is when we can do just as much as ever, but would rather not... and that suits me fine.

Happy Birthday to me.