I haven't talked with my vet about this yet, but I thought I'd see what everyone here thinks. I have two kitties, Spot and Willow. Spot is an old boy (I found him in September, so I don't know his exact age, but he's well over 10 years old). Willow was about a year old when I got her from the humane society 5 years ago, so she's about 6 years old now. Currently, I'm feeding them Precise Foundation. Should I be thinking about switching to the senior formula? What are some reasons to switch? Or should I just leave them on their current food, since they seem to be doing okay?