[Chris in WNC]

Marco is right on with his protocol of checking temperature of modern trailer tires and hubs frequently.
With Model A tires, your eyes are an important tool. look for cracking in the sidewall and between treads. If you see that, it's time to replace regardless of tread remaining if you drive long highway distances like I do. If your only driving is 30 mph to the ice cream shop or local cruise-ins you can get away with lightly cracked tires but don't be surprised if one goes south on you occasionally. Older tubes seem to be better quality, so I retain them if not checked or repeatedly patched.
We bought our blue Tudor in 2006 with tires that were installed in 1991 but almost never driven. Indoor storage kept the UV light away and they were in excellent shape. I used those tires sparingly on 3 different As over the years and they were still good when sold in 2013.
as always, your results may vary........