I just got back on the 5x5 too after I hit a plateau on most of my lifts and growth at the same time. I'm on week 3 of it and have blasted through the plateau. I still leave room after hitting the muscle group of the day at 5x5 for a few sets of pump inducing movements. It's hard to get away from the bodybuilding mentality.
At 58, how are your joints holding up with the routine?