Shame on me but I do use leather furniture cleaner and protector on my bags. They are supple and look very well. I spray my suede ones with a shoe protector (the one that Footlocker sells). My bags usually double as diaper bags and take quite a beating.
I have a rule to stay away from everything that is advertised too much. But I think a major investment bag deserves good care. Here is some advice from an article I read a while ago (as sources were cited
Coachs leather development director and one of the Green Apple founders):
1. Light cleaning an extremely diluted solution of dish soap or baby shampoo and water.
2. Heavy-duty cleaning automotive interior cleaner.
3. Softening leather honey and polishing coat.
I am not sure if I can post the suggested brands, but if the moderator gives permission I shall post them here.