Bench Press question

I was in the gym doing bench presses like I usually do, all the way down to
the chest, and then up, when over comes this trainer and says I should stop
when my elbows are the level of the bench and go no lower, to avoid injuring
my shoulders. I find I can lift more this way, and also don't feel it in my
pecs that much. Is there anything to what the trainer says, or should I just
ignore?