I found a nice graphic which illustrates the Anschutz trigger setup. The "Sear Engagment" is the most important thing and compare the 'cocked' and "at second stage" small images of the sear points.
Sorry for the confusion - 1st stage is basically taking up the slack before getting to the nitty gritty of the 2nd stage i.e. sear release. Some mechs have 1st stage spring loads and travel adjustments, some are just movement.
The thing you have to ask yourself is that once you are at 2nd stage and have applied any pressure is "has the sear moved?" and "if I remove pressure does the sear mechanism return to 1st stage?" or is the sear engagement reduced and therefore more likely to go off before you expect it to.
The AA 400 trigger tries to take you back to the safe pre-1st stage, I think. I haven't got one anymore so can't be sure.
Some folk remove 1st stage and just rely on a higher spring pressure and hopefully longer sear engagement.
Sears do wear though :-)