How often will medicare cover a new chair once you have a Dr. prescription?

I think its every 5 years, but I think I remember them changing the time limits. Curious because I am still using my 10 year old manual chair. I did get another one about 5 years ago, but I never use it. The "wheelchair dealer" screwed up the measurements so bad that it is seriously uncomfortable to sit in. I rarely use it except for when its down for the count with a flat or something like that. I argued with that dealer for soooo long. They finally took it back and gave me back a supposed new one withe exact same measurement problems six months later. Seriuosly, you should see how badly this chair fits me. Its almost laughable if it wasn't so sad and aggravating. HA! to think they still send me a 300$ bill every month or 2 for the 20% that medicare doesn't cover. OOPS.. sorry I am Ranting. haha. Does anyone know how often Medicare will cover a new chair? And yes, I am gonna use a different dealer this time.

How often will medicare cover a new chair once you have a Dr. prescription?