i rotate six of them...soak all of them in bleach for one day and put in washer for two rinse cycles..then soak in ro/di water for ten minutes to get out the chlorine smell
i only use mine after a water change for a day maybe 2 . then i dont use them at all until next water change. they are nothing but nitrate holding facilities.
I change mine every other day. I do this because I don't want any trapped food sitting in there decomposing for too long. I let them sit in bleach water for a few days then i run them through the washing machine's rinse cycle. They come out super clean.
When buying in bulk you are looking at about $2 a piece and replacing them weekly puts you at about $104 a year...not that bad when you think about it, you looking at $8 a month.