Started rotation about a year ago. I feed Fromm and rotate between different formulas. During the winter I feed the whitefish since it has less calories and keeping weight down on Mardi is important at her age and her limited ability to be mobile in the winter/snow. This is about 3 months. I switch between duck and pork also. They love all of them. I don't do a slow changeover, run out of one and start another. I'll probably feed 3 months of each.
I chose Fromm because of their great track record (no recalls) and the dogs love them.