Skis popping off when they shouldn't may be due to sloppy technique. If you're twisting your skis around instead of driving them forward and using them like they're designed you might put more torque than intended. Think about taking a lesson, and explain your retention issue. It might be a software issue.
Or it could be due to improper forward pressure, which is one of the things the shop will set in addition to the DIN. Anybody with a screwdriver can adjust DIN, but unless you get the forward pressure right the DIN setting basically won't matter. The forward pressure indicator is different for each binding, so I can't tell you how to set and verify yours over the intertubes. Spend the $20 to have a pro do it.
Then, once you are certain the forward pressure is correct, if you still feel the need for additional retention cranking it up a point or two should give you the retention as indicated by the DIN number. Understand that you are risking having the bindings stay on when they should come off. If you always ski fast and aggressive, the skis will probably come off if you crash. But if you are moving slowly (such as a slow twisting fall while standing in the lift line) you might injure yourself due to the skis not coming off.
It's a trade-off; for racers and others who are always pushing it cranking up the DIN makes sense. For recreational skiers who may ski at a variety of speeds, not so much. And if you're cranking them up due to lack of technique or incorrect forward pressure, you're not addressing the real problem.
Edited by Walt - 9/25/13 at 8:44am