Carphill007
:
Every 12 weeks or so, but sometimes I tinker at the start of the meso if I haven’t made it practical. I’m currently doing a 4 week strength block for the first time, as an in-betweener as I maintain before cutting again.
Kogre
:
The signs that it's time to change generally tend to be when you stop making progress. Some programs have a set lifecycle (8-12 weeks) and may depend on whether your goals are strength, conditioning, fitness orientated. If you work out for aesthetics and are happy with what you see in the mirror, keep at it until you stop seeing results.
I do pretty much the same exercises now as I did 3 years ago.