I'm using a Timbuk2 messenger bag (classic model) now and really like it. Very well-built, holds everything I need (I don't like to pack to much). I feel that the built quality is well enough to last me for many years. Just wish it had 2 water bottle holders instead of just 1.
Timbuk2 bags are basically bomb proof, and it should hold up well for you. I've owned quite a few of them over the years and have never had any problems. In fact, the largest messenger bag I own from them was purchased in the 90's and is still going strong.