5.5 years, in my case. There are too many variables to predict, because (1) everybody's different in terms of anatomy and exactly where your cartilage is wearing in relation to exactly which nerves are involved; and (2) people usually modify their activities first and/or take medications and/or start PT to address strength deficiencies, all of which temporarily delays progression.
Pain tolerance is also a factor; but that encompasses many variables, as well. Every surgeon who saw my X-rays since my 2015 diagnosis said he didn't know how I was still skating on my hip and assumed that I have a high pain tolerance, which I most definitely do not, because my very first X-rays showed bone-on-bone contact. I just didn't feel any pain until after getting showered and dressed, and even then, just something that I could minimize by altering my stride and, more recently, limping. Had I starting experiencing more pain sooner, I'd have had surgery that much sooner. So, you can't directly correlate X-rays or formal diagnoses with symptoms, either.
In my case, I stopped raising my leg over the boards and always got on/off the ice through the doors, and I started taking Celebrex, and then, I gradually reduced my ice time from 6-7 hours/week to barely 1 hour/week and my leg workouts from 2x to 1x/week, and reduced my elliptical training more and more before cutting it out, completely. My symptoms got better, but gradually returned during that 5.5-year period until it bcecame clear last year that I'd pretty much gotten every possible bit of use out of my hip and that I really had no choice. If I'd have waited any longer, it would have started disrupting my sleep and I'd have been walking with a cane. I'm now 10 days out from my anterior THR and doing my second post-surgery upper body workout right now, but only walking for my legs until I see my surgeon next Monday for my first follow up. Hoping to get the go-ahead to hit the elliptical and light leg workouts next week. You won't be returning to activities as quickly after a BHR; but that, and my concern over the metal-on-metal issue (and being a wus) was one of the main reasons I went with anterior THR, instead.