When I still had all 6 children at home, I kept multiples of many supplies so there was a better chance of finding one when I needed it. Now I have a can full of rulers, a bunch of tape measures hanging in my workroom, and good scissors at the ironing table, sewing machine, and cutting table. We also did this with office supplies like hole punchers and staplers. Paying for extra supplies was worth it to maintain sanity.
Haha. I accumulated 3 tape measures just because I couldn't find one when I need one. But still I sometimes end up using a carpenter's tape measure or a kiddie ruler. Haha. Scissors, I'll have to buy some more. My husband used my fabric scissors for other things, I cringe. It is indeed worth having backups especially when there are two kids (my daughter and my husband) running around the house, misplacing a lot of things.