To jump on mistakes you have to avoid getting yourself in a hole and letting the pitch avoid throwing strikes.
It's when you're ahead in the count and the pitcher is trying to paint corners but misses when most mistakes are made.
The hitters that age the best are selective, know what they can't handle and wait for that one or two pitches an AB and give it their best shot, Schmidt, Thome, etc.
The two things that kill aging hitters are chasing balls and trying to pull everything as their power declines (Howard).
Yes there may be an adjustment period, but if these hitters don't learn to be more selective, hacking away will quickly end their careers.You'd think with the money at stake, they'd be looking for every edge, but like "normal" people, a lot of players are afraid to leave their comfort zone and try anything new.