As far as Fox Evols, my opinion is they are good shocks, but they are not perfect. They use generic valving, meaning that the valving in them is the same no matter what, they don't vary it for type of riding or skill level, guess they feel the air chambers offer enough adjustment. I have owned two sets of Evols onone of my 450R's, and both times all I was asked was what quad and what a-arms. In my opinion, valving should vary based on your tyep of riding and skill level. I think that is why I was never totally happy with them. Yes, they worked well, but I could just never get them perfect. I feel they needed a revalve. Instead, I bought a set of Motowoz for my 450R and never looked back, much better setup shock in my opinion. If I revalved the Evol's I may have had a different opinion, but I feel if I buy a new set of shocks I shouldn't have to revalve them.
Service wise, I never had an issue with Evols, never leaked any air or any other problems. I just checked the air in them before every ride and that was it. The other issue you will have is if you call Fox and want to order Evol's for a 250R, they will tell you they don't make them for a 250R. You will need to determine your shock compressed and extened lengths, and then cross reference with Fox an see if they will work. Even then, I feel you would have to get a revalve to get them working perfectly.
Doug