Has anyone ran a SD-C or SD-E for any length of time in their MPX? I have both and am thinking about putting one in my MPX. I know the pistol is supposed to be hard on aftermarket triggers and was curious if anyone had used one for a while. Thanks.

I used an SSA trigger for a while, not sure how many rounds. Worked as you would expect a Geissele trigger to work, perfectly.

However I chose to remove it based on Mr. Geissele stating that it was not a question of if the trigger would fail but when it woul fail.

Eventually I put that SSA trigger in a Daniel Defense AR platform and purchased a Geissele MPX trigger. The wait on the Geissele MPX trigger was well worth it.

Exactly the same story for me. I put a Geissle in it initially, it ran fine for a few thousand rounds. Geissle then said probably won't last so I went back to stock, then tried the Timney (which I didn't like), then went to the Geissle MPX. Not 100% sure how Geissle feels about longevity on the MPX specific version since they give you a bunch of recoil springs to try and slow down the action, but the trigger itself is usual Geissle and well worth it.

I dropped in the one Sig was selling a while back - flat faced - it's a most excellent improvement over stock - does anyone know who made these and if it's one with a "limited lifespan"?

I don't know exactly what sig was selling? What they sell in their PCC now is a Timney 683. Before sig announced that product with that trigger I was looking at options to replace my geissle and had long discussions with Timney on what would survive in an MPX. Originally they said that their std. PCC 681 would be fine. But then they changed their mind (after I got one of course) and said you absolutely needed a 683. I would guess that since SIG is selling a 683 based gun its likely it will survive a decent run.