So I thought I'd reuse the nice ones on B+W, which I process at thome so I'll keep them, and use the junky ones for colour so the lab keeps them.
So I took all the spools out of all my backs and cameras and sorted them into which ones I likes and which I didn't, and thought (at the time) that I'd just grab whatever I needed before shooting depending on if it were colour or B+W.
Went to use my camera, last minute rushing around before I left: camera, check, backs, check, lenses, check, film, check, off we go. Drive an hour out to wherever and realise I had no take-up spools (or sometimes I at least had only one in a loaded back, the other 4 backs for different types of films are useless without spools).
Not once, but about 3-4 times that happened before I gave up on the idea of 'nice' and 'crap' spools, and just threw whatever in all of them so it wouldn't happen a 5th time...