Keeps things moving along and stops you getting restless watching paint dry.
I have ended up finishing 2 guitars at the same time for the third time (if that makes sense) as you always seem to have too much finish prepared for one plus if using Tru Oil it does go off if not used fairly soon after punching a small hole in the foil seal therefore best to have more jobs on the go to use it up.
Cheers, Waz