I had the same problem a couple of years ago when I had a crap chair (despite costing ~$150). I bought a chair from Kinnarps, which is a Swedish furniture company. Have a look here
http://www.kinnarps.co.uk/ , the page doesn't seem to load right now for some reason. Anyway, the chair I bought cost around ~$450-$500, and was in the middle range. When I was checking out different chairs they showed me one they called "The 24 hour chair". They said you could sit in it 24 hours a day without problems, and that it had the durability for it as well. The price tag was around ~$1200 (!).
My chair came with five years of warranty.