In general, I would say that if you find a pool which is performing well, there is no reason to move your stake. The well performing pools should have quite similar performance with one another provided they have a healthy level of stake and good uptime. However, there are a few things you would want to keep an eye on that might prompt you to move your stake.
First, you want to watch for pool operators significantly changing their fees without notifying their delegators, there is speculation that some operators might create low fee pools to attract a lot of stake, then raise their fees hoping nobody will notice. CANUK will keep an eye on the current market conditions to ensure we are always offering a fee which is fair to our delegators as well as allow us to run a sustainable pool, and we will notify delegators well before any fee changes.
Second, you want to watch for the pool reaching its saturation point. If this happens your rewards percentage could start decreasing and you should move to a pool which is not saturated. Currently the saturation point is around 210M ADA, but will change to around 62M ADA on Dec 6th.