Rubber degrades with UV exposure, even if the tread depth is ok. Be careful, esp at higher speeds.

That's not OK by any means, you don't have mandatory periodical technical inspections? This would fail immediately in any half-decent country. An example - wife's older Seat has 6 years old winter tires which were given for free when buying it second hand a year ago. Technician just told us even those are beyond acceptable here in Switzerland and we need to change them before next inspection.

Your very old tires makes you a serious threat on the road while completely oblivious about this fact... not cool, please change them if you drive on public roads, if not for you just for the sake of others.

We are in Germany, which has the highest inspection standards. The tires have passed every inspection. They look like new, but I will still replace them soon, just in case. I am writing this because most people cannot imagine that a 900 kg car puts very little pressure on tires, so they are hardly used.

Beware of dry rot. Rubber that old is likely not in as good shape as it might appear, and could fail catastrophically in the right conditions.

Seriously, you should not use tires older than 10 years. They degrade over time.

Time based degradation is mostly a factor of exposure to the sun and the weather.

I just trashed some 15yo Firestones last month, after wearing them completely bald of course.