The life of a film reviewer, with its weekly routine, sometimes has a deceptively Groundhog Day-ish quality. It's easy to think time is standing still. The same sorts of film come around. The same stars come around. Johnny Depp? Back in another movie, looking pretty much the same as ever ... Cameron Diaz? Back in another movie, looking pretty much the same as ever ... And yet time is naturally not standing still. People are getting older, careers are waxing and waning. Suddenly, with a jolt, you realise the young stars who 10 years ago you thought were going to be ubiquitous are no longer around. Wait! Hang on. American Beauty – Thora Birch, Mena Suvari, Wes Bentley? Where the hell are they? Well, they're still there – IMDb reveals they're steadily working, though they're not as massive as their initial career-trajectories appeared to promise. But any one could still suddenly come storming back with a new role — and we will be stunned to see they look a lot older, and to realise that we must be older too.

My life is full of these jump-cut moments. I sat down this week to watch The Messenger, about two soldiers whose grim job it is to notify civilians that their loved ones have been killed in action. One of these soldiers is played by Woody Harrelson – the sort of actor who gives me that soothing, Groundhog Day, time-standing-still feeling. Basically, Woody Harrelson looks the way he looked 10 or even 20 years ago. But that other guy – grizzled, careworn, in his 30s, with a low growly voice that sounds like Ray Liotta's or Jack Nicholson's; the one who's beginning to go bald. (This last effect has been created artificially.) Who is this guy? Oh no. Surely it's not young Ben Foster?

Now Ben Foster has been working continuously over the past decade, and doing good work too. He's 31 and doesn't look particularly older than that. But my problem is that I keep remembering him as the lovestruck, heartbroken teenager from the sparky and entertaining high-school movie Get Over It from 2001. And the reason for this is that Get Over It had a terrific, single-take sequence over the opening credits; it shows Foster's character stumbling, stunned, away from the house of his now ex-girlfriend. She has just dumped him, and heartlessly given him a box of his stuff to take away. As he trails off, a huge fantasy cast sing and dance behind him, ironically, to Captain & Tennille's Love Will Keep Us Together. Over the years, I've been playing this sequence on YouTube every few months or so. If you've never seen it, or even if you have, watch it now:

Great stuff. And all this time I've sort of assumed Ben Foster is that age still. But here he is in The Messenger:

Of course he looks older. Why shouldn't he? Yet something about the film business, which freezes people in time on celluloid, and in some cruel cases causes their careers to suddenly vanish, distracts us from this basic fact.

Watching that Get Over It clip with its parade of names is interesting. Kirsten Dunst ... yes, she's still going great guns, and even bagged the best actress prize at Cannes this year for her performance in Lars Von Trier's new film. But Melissa Sagemiller? Where is she now? Erm, working, doing series television. She should be bigger. Shane West? Again, really funny. He actually played himself as one of the young stars being tutored in poker by Brad Pitt in Ocean's Eleven. And now? Same kind of thing. But wait – there's Zoe Saldana … I don't remember her in Get Over it, but she's big now. And there's Mila Kunis! The Mila Kunis who almost stole Black Swan from its Oscar-winning star. Was she really in Get Over It? Apparently so.

The film industry, pestering us to watch the hot new film with the hot new star, is one that only seems to live in the present, and the realisation that time is passing – always a trauma – is especially uncomfortable in the cinema. I remember in 1999 watching a film called Gloria, a remake of a Cassavetes picture in fact, featuring Cathy Moriarty. Stunned, I realised that this was the Cathy Moriarty who was the incandescently beautiful and sexy Vickie LaMotta opposite Robert De Niro in the 1980 film Raging Bull.

After the lights went up, I spluttered almost indignantly to the Standard's film critic, Alexander Walker, that I couldn't believe how much older she looked. "No, Peter," Alex said drily. "What business has she getting older? After all – look at us!"