It depends on the canister size, bioload, etc., but I personally do not clean out the canister every WC, probably only every 3-4 WC's at least. Just keep the water parameters in check, thats what matters and how you should decide your schedule.
Any filter is ideally cleaned at least once a month. If you wait longer the debris will breakdown and the filter will become a nitrate factory. HOB, canister, anything should be cleaned monthly. Theoretically a water change will not alter the bacteria in the tank at all so cleaning the filters at the same time should not be an issue.
A lot will depend on stocking, tank size, number of filters and what's practical. Although cleaning your filter more frequently to remove debris before it breaks down is a great idea. IMO the only way you really would benefit is from weekly cleanings, though this would be very impractical. Much more effective to just do weekly water changes to control nitrates on a fresh water tank. Overstocked, undersized tanks will definitely need more frequent cleanings. While large tanks with multiple filters can go longer between cleanings. Heck there are many very experienced fish keepers that go many months in between cleanings but this doesn't mean it will work for everyone.
In my case my 450g has a sump along with two canister filters. I clean only one of the canisters every month, so each of my canisters get cleaned every 2 months. Now if I were to have the same stock in say a 180g tank with only one canister. I would have to clean it at least every 4 weeks, maybe even more frequently.
Best bet is to just be the judge yourself. Gauge the cleanings by how dirty it is when you do clean it. Also depending on your water change schedule, if you are one to not what to do a lot of water changes, then you may find more frequent filter cleanings suit you best.