*Canned Cat Food* What do you use and how often do you change flavors/brands

[MikeAk]

I have been reading a lot of information on how it's a good idea to add different flavors and brands of food into our cats diets in order to limit the possibility of nutritional deficiencies. As it is right now we only feed our cat Wellness canned chicken(grain free) and every couple of months Dick Van Patten's Natural Balance Ultra.
I was wondering if I could ask what everyone uses and the schedule they use when changing it up?