I used to organize by photo number- but then I started using Journal Cards in many of the photo places so that messed me all up! Plus I have favorite designers from a few different stores- so sometimes I need a specific store's template.
I switched about a year ago & reorganized them all by designer.
Sometimes I delete if I know I'm not going to use it again- other times I just file it away. I do re-use a few faves for sure!