As I have over the last 4 years got fitter and much more flexible (spine wise) I have found that I have adjusted fore/aft saddle position and as a result had to change the saddle height as well. I am now a fair way remote from where I started out. So if you are a super athlete and your riding position is unlikely to change then you could be ok but speaking from personal experience if I had bought a bike with no seat post adjustment then I would be goosed, and looking at an expensive "upgrade".