When a food says "for all life stages" it means it has been fed to a number of dogs of various ages, and they all survived in basic good health. Notice, I didn't say HOW many dogs, or WHAT their ages were, or HOW long it was fed. Most foods can say that their food is for all ages. Senior dogs in GOOD health can eat pretty much any good food out there. Some people think that senior dogs need less protein for their kidneys, but I am not that educated about that.