I had my bindings re-mounted on new skis this year at REI (cheapest option). Put my height and weight (about 5'7" 150lbs) , lvl 3 skier, and they put me at a fucking 5 DIN. Let me repeat: FIVE DIN!!!
Honestly, I don't know too much about bindings, but they did do a torque test so I assumed they kind of knew what they were doing (I don't have the highest quality bindings, maybe the display was just off). However, the last few times I've been out, my skis have been coming off in the dumbest fucking ways (like landing, balanced, after dropping a relatively small 8-10 foot cliff). This past weekend, I did a normal stop, kind of aggressive, and hit a small chunk of ice. Both my skis ejected, and I flew down the hill like a retard at ~30 mph. On that cliff drop, I had hit a rock shallowly buried under the snow, which caused me to slam down on another, fucking up my hip.
That was the last straw I guess. I could have tightened them myself, but last time that happened, I snapped a tibia. Brought them into the pro shop or whatever you want to call it, and they basically doubled the DIN.
I'm not completely sure what the moral of the story here is... I guess don't get your shit done at REI? Yeah, I don't trust them.