I've only had mine for a few months, but if you've got deep enough substrate, isopods, and springtails, I don't see why you would ever have to clean it.
I'm keeping and breeding mine for about five years know. I never cleaned anything (besides the walls of the plastic box), only filled up some soil and put some more bark pieces on top. My banana roaches have about 12 inches (30 cm) natural soil from broad-leaved forest with much microorganisms, springtails, earthworms etc. inside. Food is only given as much as they can eat in some days. There's nothing to clean, no food leftovers (= no fungi) and it doesn't smell at all. Banana roaches will not breed in boxes without soil.
Its all fun and games till you try to feed them in a non screened cage. I think i might have to make a feeding both out of a 10 gallon or something. or stick them in the fridge for a few min so they go in slomo.
We advise our clients to use 3 gallon buckets. The square plastic ones often used by florists. Plastic paint buckets just square. We recommend 3 gallon sizes so they can be placed in the refrigerator as needed for slowing them down.
To clarify we recommend the buckets as housing for the green banana roaches, and placing the buckets in the refrigerator to slow the roaches, not the buckets down. We have found that bucket speed itself is unaffected by temperatures.
Mine are breeding well w/o soil. I didnt know this and have been raising them in a dubia-like container w egg crate and feeding cricket crack and oranges. Ikeep a small cup of water crystals in as well. Guess mine don't read the board!