Do tires for collector cars last forever?   How often should they be replaced?

There is no conclusive evidence on an absolute life span of a tire since there are too many variables involved to give a definite answer.  Always inspect your tires for weather cracking, dry rot, visible cuts, bulges in the sidewall, or cracks in the tire.  If any of these conditions are present, your tires should be replaced immediately.  It comes down to your confidence in the tires--If you feel they need replaced, get them replaced!