When I was writing for the restaurant magazine, I learned about something called par levels. What that meant is that a restaurant would set a minimum level of a particular item and never go below it. For example, they might have 500 cloth napkins as the par level. Then someone I know who is a nurse told me that hospitals have par levels so they never run out of a particular item.
The only par level I have in my home is laundry detergent. I've vowed that I will always have the bottle I'm using and a full backup. That's because there's no replacement for it. I don't want to pull an I Love Lucy by trying dish soap in the washing machine. I know it's the same with dishwasher soap, but I can live without a dishwasher, not so with a washing machine.
So I broke my own rule and am down to about one capfull, one load left, with a whole bunch of laundry so I'll have to get groceries tomorrow. I'm still not used to how much laundry detergent costs.