They don't have a smell. The smell would come from uncleaned urine/urates or poop, which should be cleaned thoroughly anyway (assuming you use paper towel for substrate) each time they let something go. If you want to spot clean and then clean thoroughly a bit less, every other time or longer, using aspen would be better.
How often you clean totally depends on how often your snake pees/defecates. It varies anywhere between once a week to once every two months.
Where you live and the humidity of your home is important when choosing substrate... For example, my home's humidity is 60%, so using aspen (a drying substrate) is totally fine, while using coco fiber is WAY too humid for me and also has a dirt smell. Aspen is also cleaner than coco fiber and doesn't stick to everything.
BP's will only need to eat one appropriately sized meal every week~2 weeks as they get older.
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