Typically, if you are making a change to your lifting form you have either stopped making progress, or you are working around an injury. I have always advocated to stay away from making drastic changes in form, but rather continue to make small tweaks as necessary.
Along with the change in form, it is also important to continue to evaluate your weak areas. Your assistance exercises should be planned to strengthen those weak areas. Is it your lockout in the bench? Then you probably should work on triceps strength. Is it your lockout in the deadlift? You may need to start training some exercises to strengthen the posterior chain.
I always like to give a change in form enough time to evaluate and perfect the new technique. This may take an 8-week training cycle or two. One of the most important changes in form that I ever made was in 1996 when I decided to move my very narrow deadlift stance out about half a foot. When I decided to do this, I added a steady diet of front squats and leg press to strengthen my legs. This allowed me to maximize my leg strength to gain an explosive drive off the floor. If I can get a heavy deadlift above my knees, while maintaining a good back position, I rarely miss.
Brad Gillingham, CSCS