Luckily they test shock/strut function at the annual inspection. If it's below a certain percentage, your car fails.

If they don't do mandatory inspection in your country, you're sharing the roads with death traps that could crash into you at any moment because who knows if they even have brakes. In that case, who cares about worn struts?

Anyway, from experience, original struts are usually good for 200-300k km but I've seen more than that and still good. On mostly German cars. Of course if you see an oil leak from a strut you should get that pair replaced immediately. At that kind of mileage, you get a handling improvement if you replace them before outright failure, but they're not actually dangerous at anything resembling sensible driving.