Sorry to extend this thread, but MUST say THANKS again.
I pulled all wheels off tonight to take in for the new Maxxis E's (two dealers told me the wheels I have would be fine going to E from D (only an 80psi vs 65psi thing as trailer still weights same 8-9K)).
Good news is that the spare looked perfect even though it was 10 years old. Lucky news was that all 4 running tires had several 1/2"- 3/4" cracks between treads on each, with one tire having a several inches long crack running between treads (all cracks ran along tread on top surface with one tire also having several small cracks near the tread on the side-walls).
I take back my previous comment about probably being OK. I count myself fortunate and don't planning on running 9yrs again.
Ron