Hello!
I, too, suffered slipped epiphysis w/my right hip when I was 12. Had pins, a partial, then finally a total when I was 23. I'm now 45, and here's the good news: for more than 20 years, I suffered no pain, very good mobility, and a very active busy life. I've had two children (born when I was 37 and 39) and I had no problems w/my hip w/either pregnancy or delivery.
My suggestion: do not live with the pain if you don't have to. More and more docs are realizing that young people deserve to have the active and pain free life a new hip can provide.
The downside of being a "young" total hip recipient: all things indeed wear out, eventually. I'm facing a total hip revision in two months. But keep in mind, I had the "old style" hip replacement more than 20 years ago, and although my surgeon did an excellent job, i'm now told that after years of wear, the polyethelene particles shed microscopic pieces that can affect the bone beneath the cup and cause a condition called osteolysis (basically, the bone starts dissolving).
Newer hips are now using ceramic and also something known as cross-linked poly, which apparently has greater wearing power and not likely to break down.
So, in a nutshell, i've had 20 great years w/my total, and yes, I couldn't jump around and be crazy, but so what? Few people even knew I had a hip replacement. Basically, be sensible about the types of activities you do (nothing high impact like running or tennis) and try to keep your weight under control. I know the outcome of the revision i'll be having soon is not likely to be as good as the first hip, but hey, i'll hopefully be in less pain than i've been in in the past few months, and i'll be able to start up walking (the only excercise I can really stick to!) again.
Good luck with whatever decision you make! - tracey