Lots of discussion to replace tube each tire change. I'm in the school that replaces with a new one each time, on a road bike. I do not want any chance of an old stretched tube getting a crease in it and losing air on a nice day riding or when I want to get somewhere.
The dirt bikes where patched and repatched. They always had a crease somewhere. But I was never very far from transportation and would ride them flat.
2 favorite signs:
CAUTION we do not dial 911 first
CAUTION if you can read this U R in range