3 months for me. I have 2 canister filters (Fluval 306 and SunSun 302) and they are cleaned first and last week of the month.
I only rinse the bio media with tank water as well as the foam pads on my fluval. The SunSun has the blue filter pad (Marineland blue bonded pad) that I toss and replace with a new one. I have Purigen bags that I regenerate and replace into whichever canister is up for maintenance.