It's true that I had not considered I would drive off with out having locked the drawers, so I had not had the problem with the drawers sliding open (over 20 years as a road tech), and as far as "center of gravity" that seems to me to be a function of what tools you put in what drawers. I do use a couple of GI canvas hand tool bags to handle the tools that I use 90% of the time, and also have some canvas bags for groups of power tools (all my drill bits and drill in 1, dremel and bits in another, soldering tools in a 3rd etc...).
My experience with where my tool boxes fail has always been that the supporting welds between the upright and drawers or the brackets that hold the drawers eventually fail from bouncing up and down over a few million miles, but in general I think it is fair to say that the box usually lasts as long or longer than the service van.