Mostly because I don't like having to crawl around working in the sump if I don't have to so if they're working ok I let them do their thing. I suppose partly I'm lazy but I also have hip, knee, and back pain that makes crawling around in the stand and getting back up a very unpleasantness experience so I try to avoid it when I can. I have a rolling stool I use but I have to actually get down on the floor to swap out a return.However, I have to ask, why would you not clean such a critical device for 6 years?
TLDR I'm old and it hurts to crawl around

