Two years for me using Nature's Gate Organics shampoo. Almost that long for Sauve Tropical Coconut conditioner (or whenever it was introduced, can't quite recall), and also LA Looks gel, although I recently switched to LA Looks sport gel (has even more hold). It's great having found products that work! Every now and then though I will try something new, especially in the summer when I battle humidity.
I have 3A hair. I've discovered Jessicurl shampoo and Too Shea conditioner and I'm thrilled! Long-time LA Looks sport gel user.