Dominik Bindl / Getty Images

There's nothing more sobering than realising your heroes are getting old. And there's nothing more sobering than realising you are too.

I remember when a wizened Christopher Lee appeared onscreen as Saruman in The Lord of the Rings -- it was a near biblical moment for my Dad. Here was the iconic villain from the films Dad had grown up with, from Dracula to The Man with the Golden Gun, booming on screen as Tolkien's great wizarding villain.

It was a stroke of genius casting that resonated with a generation of moviegoers.

When Lee died in 2015, the moment was felt by a generation too. But for those of us who came to The Lord of the Rings as nerdy teenagers, this was just another icon from a bygone time. A sad loss, but an actor from another era dying after a life well lived.

But that age gap doesn't last forever. And you know you've truly grown up when you start losing your heroes like they were friends.

On Monday, the world mourned the death of pop culture icon Luke Perry who died a week after suffering a massive stroke.

This wasn't a silver screen starlet or an old war-era crooner. This wasn't your grandma having a glass of sherry while she put on Sinatra's old records whilst remembering the Rat Pack days.

This was Luke Perry. Dylan flippin' McKay from 90210. The boy you were absolutely going to grow up and marry if only you could get a plane ticket to Beverly Hills and get Brenda Walsh out of the way. The swoonboat you stayed up to watch on TV with your older sister (who was also planning her wedding to Dylan in the idyllic surrounds of the Peach Pit diner).

And he didn't die in a car crash, like that erstwhile white t-shirted dreamboat, James Dean. The James Dean of the '90s died of a stroke aged 52.

Luke Perry was a man for a millennial generation (even if he only scraped in by virtue of the fact that he was a 20-something actor playing a high school heartthrob). He was the pop culture icon of an era. Entire schoolyard lunchtimes lived or died based on what had happened on TV the night before between Dylan and his latest flame. When it came to fictional couples, his was a face that launched a thousand 'ships.

And he stayed a heartthrob even as he grew older and moved away from 90210. A whole new generation found him when, as a father himself in real life, he starred as Archie's father Fred Andrews in Riverdale.

People were tuning in to see Luke Perry on primetime TV and they were drooling over his son instead? The younger me would have never believed it. (And Molly Ringwald, Perry's onscreen wife in Riverdale? Wasn't she literally just in The Breakfast Club, like, two years ago? When did she get old enough to have kids?)

But time is ruthless. We're getting old, and our heroes are getting old too. If Luke Perry can go, then none of our heroes are safe.

One day, I'll tell my kids about the loss of those '90s heartthrobs and they'll roll their eyes before turning back to their HoloPhones -- certain that no stars they love, no Marvel heroes or geek culture icons of their generation will ever grow old.

But they'll have their Luke Perry moment. You always get a glimpse of mortality at times like these when you realise that you can't go home again. But in my case, I'll never be able to go back to the Peach Pit.