It depends how much time you have for the ascent. When people try and rush to the summit on the first few days of their trip, their chances of getting AMS are unacceptably high. People who spend 2 weeks over the whole trip usually have a very good chance of acclimatising well, summiting safely and even enjoying the tough summit day. Climbers on 6 day trips usually acclimatise sufficiently to safely attempt the summit towards the end of the week but everyone is a little different when it comes to high altitude acclimatisation and the important thing is to listen to your body and act accordingly.
