I suppose you could use a shore durometer to determine the (remaining) elasticity of the tire. That said, you would have to know the durometer reading for your specific tire when it was new.
Also, for methodology reasons would you have to take the tire off the rim to properly test it? I would guess you would. If you go through the trouble of removing a tire you may as well put a fresh one on.
Durometers are about $300.00 or so, but there may be cheap ones out there. I dunno.
You also have to factor in UV exposure, too.
Frankly I would listen to the 6 year lifespan and plan accordingly.
Also, for methodology reasons would you have to take the tire off the rim to properly test it? I would guess you would. If you go through the trouble of removing a tire you may as well put a fresh one on.
Durometers are about $300.00 or so, but there may be cheap ones out there. I dunno.
You also have to factor in UV exposure, too.
Frankly I would listen to the 6 year lifespan and plan accordingly.