I bought an 18 year old Land Rover some years back. It was on it's second set of tyres. The owner, who had bought the truck new, told me he only replaced the tyres about 10 years earlier because one of the originals had blown out...

I drove straight to the tyre fitter for a third set. The tyre guy could not believe how brittle and stiff the tyres he was taking off were. Given that I would have been airing down a lot for sand driving the old tyres couldn't have lasted long.

Don't drive around on old tyres. Your insurance co might not care, but neither will you if you are dead.