heat exapansion vs cold contraction probably. Something might be on the edge of worn and when cold demonstrates an issue, then heats up with use and expands a little. That or its sticky in there and the cold is preventing the release bearing from moving up and down the collar super easily until it heats up.
Like the ASE page shows, it could be anything in the bell housing. Are there any noises at specific times? are you hearing any grinding or squealing with clutch in or out? that will help us narrow down causes.
How many burnouts have you done on this car? be honest now
as far as longevity, its possible to milk a clutch problem for a looong time, just so long as you never fully trust the car, like no really long road trips.
Im sure you could wait to christmas, but no more street racing till then.