It's common for trainees to jump from programme to programme, feeding off of the novelty that comes from doing so. This novelty can fuel motivation to train, as well as enjoyment of the process of training. However, it comes at a cost.
When we change our programming too often, we limit our ability to adapt to the stimuli applied. This often manifests through repeated soreness during training and suboptimal progress in strength, and in some cases, pain or injury.
On the other hand, this does not mean that following the same programming all of the time leads to the best outcomes. In fact, doing so might lead to reduced motivation to train, complacency, and once again, pain or injury.
What we really want is the following balance:
1) Enough novelty to sustain our desire to train and present the body with novel stimuli to drive adaptation.
2) Enough consistency to allow sufficient time for those adaptations to occur, as well as skill acquisition in the movements performed.
In practice, what this generally looks like is a duration of 4-12 weeks as a minimum to maximum range of commitment to a specific training phase. There may still be some modifications to volume and intensity during this time, but exercise selection should mostly be the same.
The rationale for this range of time is primarily pragmatic in nature:
4 weeks is long enough to allow for acquisition to any exercises that have not been performed for a while, and soreness should also be mitigated within the first 2 weeks. This is probably a bit short of a period of time to change every exercise, but you could change some of your movements for sure.
12 weeks is just about as long as anyone is likely to continue progressing some sort of training variable without excessive fatigue. For most individuals who are training with the intent of progressing effort, reps, sets, or other variables across a phase of training, trying to do so for longer than 12 weeks is likely to be unsustainable.
If you are constantly chasing novelty, you may be leaving results on the table. If you are constantly on the same programme, you probably are too...
