I recommend staying with your favorite one; however it is ok to have a short form and a long form. When I sit and meditate, I use my long form, when I am on a bus, passing by some people on the street or whatever, I do a short form. As we have said to all of you, as a special mindfulness activity, when walking into a building or a hall using a short form is fine. So I have two different forms.
It is good to stay with just one long form and just one short form. If you have a lot of different forms, you are going to make yourself confused. It is like, "What should I wish this person?" and we are lost. Then we are into restlessness instead of into meditation. So to have a set phrase that comes out easily, and smoothly, quickly, etc., it is very helpful in that way.
Also by keeping one form, there will be less likelihood of confusion when the mind is scared or afraid, at the moment of death. Some of you have heard that when I have had dreams that were supposed to be nightmares, I would sit down and I would start doing Compassion/Lovingkindness meditation in the dream, I get ready to die. For me that is automatic, it has happened in many dreams that were supposed to be nightmares, I am not afraid, I just see that "Ok, I'm going to die now", and I immediately sit down and start doing Compassion/Lovingkindness meditation; it is automatic in my mind. Some other meditators that I know have something else that automatically comes up in their mind when they have those types of nightmares do to having a set phrase, a set way of doing things. That is very helpful because then it can come up quicker when you have a limited time to really think about making a decision. I don't want to have the thought, "Oh, what should I think now?" as the airplane is shooting its rocket straight into the building I am in... You haven't much time. So to have something that is a set phrase, especially in the Compassion/Lovingkindness wish is very helpful.