just a complete noob point of view here...take it for what its worth.
for the past 3 years I have been doing pretty much same lifts...only variations would be swapping from DB's to BB's, swapping machines for freewieghts....and obviously playing with reps counts and STR's.
However, I recently started working out in a different way, doing exercises I have never done before....while my numbers aren't jumping up right now (learning the proper way to do these things...someone earlier posted on "having to learn new methods" or whathaveyou as being a bad thing....I think the opposite.) but once I learn and these "weak spots" grow....my numbers should skyrocket.
I will attest to the "train to your weakes muscle" mentality. I had no idea of the weak spots I had until now. Weak sucks. LOL. But I left my ego at the door when I asked for help....so it's only up from here.