Buying another box, bag, etc. of soap, toilet paper, tooth paste and whatever long lasting product before it runs out. It doesn't expire (fast), therefore I always have a second, full bag as a buffer, and as soon as I have to open the second one, I put it on the shopping list so there is always a buffer bag and I don't get annoyed if I still forget to buy one or it's out of stock.
It's been years since I had to use some weird substitute for toilet paper.
Can't get my partner to do this. They are too worried about "saving money/we don't need it (now)". For heavens sake, I'm not saying buy a spare house; just pick up an extra tube of toothpaste!
You can tell them you're not wasting any of it because eventually it will be used, none of it will get spoiled and people tend to actually need that bog roll within a week or two. Also, it's a ONE time "double" buy, because from then on you buy everything once just the same; you just make sure you don't end up spending even MORE when you run out of the 24 roll TP bag and have to quickly buy a less eco 6-pack.
We are both university grads and know how math works. They just can't get past the psychological barrier of "the bill will be higher when we check out".
I'll let them know that (in case it ever becomes relevant).
They are a wonderful partner and I would never leave them for something so minor. It's just a thing I can't quite wrap my head around - I'm sure I have things about myself that they don't get either. It's not a big deal to either of us.