I use to train regularly and over a period of a number of years at four different dojos. It can get a little addictive if you are at all connected to the 'community' of a dojo and start to have any feeling of wanting to go to practice in order to see the people and see where their aikido is going. In fact, it can become something like a strange social obligation.
In any case, I think it was ultimately great for my aikido if only because it increases the number of hours that I trained and the number of people that I trained with, and both of those are basically good things.
My teacher (the teacher with whom I did tests) insisted on two things, both of which seem reasonable to me. First, that I think of myself as his student and I have a clear sense of commitment to him. Second, that I do not skip classes in our dojo in order to go to classes in another dojo. Of course, the second rule wasn't some sort of black and white stricture. It was more like a request to show my commitment to his dojo by giving it priority and to understand my responsibility as his student to being in class.
Of course, if I didn't like the rules, I was free to find a different sensei, and he would have happily welcomed me as a guest.