My personal trainer gave me this amazing program that I've been using for like two months. However, last time I ran into him, he said that I should change it and try new work outs because my body is going to eventually get "used" to it and it needs to be "shocked" for it to advance and grow muscle mass.
But isn't my body going to be "shocked" if I keep the same program but lift heavier weights?

Basically my question is: Do you guys keep the same program for months or do you frequently change?