Aged aircraft tyres tend to exhibit signs that they are reaching the end of there life.
Firstly ageing crazing and cracking of the side walls.
Secondly splitting between the treads exposing the top layers of the carcass.
The above (other than cuts) are the only reason we ever replace nosewheel tyres on our helicopters. Other than taxiing there are no loads and wear is negligeable.
There is no comparison between the stresses on a car tyre and a light aircraft tyre.
The tyres on our 150 are around 18 years old and serviceable, however the inner tubes have been changed a couple of times purely for peace of mind.
Our experience is similar to some of the posters above. One owner/pilot, a mix of grass and tarmac.