Thought those $12 Amazon rubber focus rings were junk, then a guy in Toledo showed me his 6 month old one still going strong | Camera Repairers - Talk Freely
I was in the same boat, figured those cheap rings would stretch out or get loose after a month. Mine's been on my 35mm for like 4 months now and it still snaps on tight. The trick for me was wiping it down with a little soap and water every couple weeks, sounds dumb but it keeps the rubber from getting greasy and slipping. I also stopped yanking it off by the tab and just roll it off slow. Maybe it's just me but the cheap ones hold up fine if you don't treat them like a $50 ring.