How long is the glue good for on your 'spare race tire"…seems that if you never got a flat, it would eventually dry up then if/when you did mount it/need if , you would have a poor contact surface and no glue to boot(if it was being used in a race)…or do you add a little glue before every race (which would then lead to a BIG glue buildup). Is this a problem?
In the event of a flat you are pretty much relying on the “tackiness” of the old glue and air pressure. I wouldn’t worry about the glue getting old because of air pressure but you would always add a new layer of glue to bring back the “tackiness.”
I had a spare sit around for over 24 months and it was good for 35km in a RR.