Aw [censored], I'll bring this one back from the dead.
After 24 years of driving, I finally had to use the spare and of course it's a donut, as it would be in most cars. I guess I'm lucky.
Ok, bottom line: call the manufacturer of the compact spare and ask them what the shelf life is of such a tire.
Then if you choose to keep the compact as the spare, and it is deemed that the compact tire should be replaced, you must find a shop that has the proper equipment to mount a compact tire onto a compact wheel.