Double V Wheel Questions

Did a search but couldn't find the answer, so I apologize if this has been asked and answered a zillion times. Here goes.

I primarily need a non-steel double V wheel that can carry reasonable loads (within its spec'd limits) but doesn't develop flat spots after months of being stationary under said load.

I don't need critical accuracy at any time, except for no flat spots - ever.

Delrin or polycarbonate? Or something else (besides metal)?

Speaking of poly double V wheels, while...

Double V Wheel Questions