Yeah, I always show up when the movie actually starts. I know that AMC lists the actual start time along with the showing time. This usually happens on accident anyway, my friends are always late to show up to carpool anyways

With my luck, specifically that screening will be ad-free and I'll miss a lot.

I went in like 15min late, there was no-one to inspect my ticket so it felt criminal to let myself in but I went in regardless and had a good time, saw only two ads though

Not OP, but I used to always have to show up early so I could get good seats — why do the rows just feet from the screen even exist — but I guess now that selecting seats when you buy your ticket online is normalized, it isn't usually necessary. Hadn't considered before, though tbf I rarely go to the theater.