I'm thinking about buying one of these belts (Wilderness Instructor, probably the Easy Fit model). It seems to get good reviews, but my one question is this: I see that it uses a "pressure retainment" system, rather than using fixed holes. That being said, how well does the system work? Does it stay where you set it until you manually loosen it, or does it tend to loosen itself over time as you go about your business throughout the day? I haven't read any reports of this happening, but I just want to be sure before I buy.