Okay...this is a matter of debate, I bench press for competition year around, and I do not warm up....just stretch...and when I'm under the bar...I never really know what my max is till I hit it.
You see leading up to competition I work out like this.....
5 sets x 3 reps till I fail at top. Meaning if I get all reps in the sets I move my top 10 pounds.
Then 2 months before I work out like this...
set 1x6 reps 65% at what my max should be on a rep/max chart.
Set 2x4 at 80%
set 3x2 at 85%
Set 4x1 at 90%
Set 5x1 at 100%
Set 6x1 at 100% + 5lbs. (this then becomes your new max)
But since you did it in a pyramid you never really know what your 1 rep max is till you hit it at comp.
I start at the last 100% + 5, then go up by 10 lbs. for my next 2 lifts.
It's a mind thing...I never go in knowing what I will or can get...till I do it. If you don't fail before competition in the gym....then when your on stage you never really know where your at. Just a trick I use.