i have a question regarding range of motion for certain exercises. i have seen clips of bodybuilders such as levrone, coleman, cutler, johnnie jackson, dennis james and a few others shorten up the range of motion a little.

bench press, they may touch and to 3/4 reps, or not touch and lockout
db bench, 3/4 reps with the dumbell

leg press, there legs bend 90 degrees and then press back up

shoulder press, chin level then press up

dips- 3/4 reps

squats- parallel then back up

pull ups, 3/4 reps

stiff deads, going down a little past knees then back up
there are a few more exercises that they do this and i know they arent the authority, they do know what they are doing to a certain extent.

my question is perhaps i missing something in my training? should i be shortening the range of motion up allowing me to use a little more weight and get more reps????? currently i do more of an extreme stretching for each of the exercises do the FULL range for all of my exercises.

what is your take on this??