I never load them until I get to the range, belt on, gun on, then load my mags when I get to the first stage.
Few reasons,
Don't really want to/ sounds boring
Usually drinking beers with buddies night before
Usually just ate some killer BBQ
Meat sweats and loading mags=dropping bullets everywhere.
Seriously though,
It only takes a few minutes to load up a few mags. If your concerned about inspecting every bullet before you load, you should seriously reconsider your ammo loading habits. Your not gonna check every round all day long when you load up. Why the first set of mags 12hrd sefore you go to the range?
I'd just prefer to do that when they come off the press. Once they pass the case gauge and I see the primers are good, they go into organizers if im flying or a ammo can if im staying local.
I use 3 mags all day, 1-170,1-155,1-140. Unless the stage requires otherwise. Only ever have to clean the 170, its usually the only one that hits the ground on most stages.
Everyone has their own ways of doing things, ill never tell anyone their way is incorrect. Especially when it comes down to pure habits.
Are you having fun with your buddies on range day? Thats all that matters, rest of it is window dressing.