I have done this for many years and I think it is necessary from a mental aspect as much as physical. I followed strict programming for my first 15ish years of training and then decided to start working in an 6-8 week period 2x a year where I essentially did as I pleased in the gym- and currently am in one. It is very liberating from a mental standpoint and makes me feel refreshed.
I end up still generally sticking with the big 6, but one week I may do an OLAD, the next add in a bunch of HIIT, maybe do a week of traditional programming, etc.. Just depends on how I'm feeling.
Then at the end of 8 weeks, I am craving a routine again. Win/win.