I've seen many assertions about Propecia long-term, but I can't find any decent data one way or another. I'm just a single case, but I've been on finasteride for six years and I'm still holding my ground. I'm on quite a few other things as you can see from my regimen, and a few things not listed, because they aren't taken for hair loss. If I had to give up everything but one medication, I'd keep the finasteride. Based on the rapid progression of my hairloss prior to starting finasteride, I'm convinced that I'd have no hair in my crown without it. The front is transplanted, so that area is stable.
Prior to starting finasteride, I had been on topical retin-a, azeleic acid, folligen, monoxidil, Dr. Lees 11.5% micronized minoxidil without betamethasone and they didn't seem to do much for me. Spirocream from Lipoxidil is the only thing that actually grew hair, but it fell out after hair transplants never grew back.