Tbh we wash them and use them for really dirty stuff. Like when you need to remove mold with a chlorine spray or poop from your shoes. Then they get tossed because there's no way I am washing that again.
We're phasing out single use sponges though, but now I don't know what to use for the really dirty stuff.
Hot take: there is no food safety reason to replace a sponge if it's still good at removing food from dishes. If you remove the food source, and the soap removes whatever is living on the dish, whatever is left over will die due to lack of nutrients and water. It's why in food safety courses you are taught that dishes have to dry completely. Even a sponge which has been used once will be depositing "new" pathogens onto the dish. Stuff is gonna live in the sponge. The sponge doesn't kill pathogens. Removal, soap, and desiccation do. The sponge's job is almost purely mechanical.
There is absolutely a food safety reason to replace a sponge. Most bacteria don't just die when they're in dry nutrient poor environments. They desiccate themselves into a spore form. Those spores can stay like that for very long periods of time until their environment becomes more wet. Then they can continue their lifecycle until they dry out again. Dry doesn't mean sterile.
Longest I ever kept a sponge for was four months it was a "I'll do it later" kind of thing, the green scrubbing part had nearly fully been removed lol.
Bro my happy time place now is hardware stores. Similarly would you believe Lowe's and home Depot around me both don't carry garage door track sections? Baffling.
Yep have done this for years. Cut a corner off a sponge each time it enters its next life phase so you can easily identity the phase it's in by the way it looks.