I don’t have an answer for when to get a new cat or age of new one.
I would like to address the dry cat food “problem” which has never been a problem for us. We have 2 senior cats who won’t eat wet food...yes, we’ve gone through this many times. We feed Orijen original red and we have had best luck with it. Price is outrageous, but they both like it, their coats glisten and they do great. We do, however, strictly monitor how much they get fed so they have never been overweight. They are allowed to graze at will but I never exceed their recommended daily allotment of food. As to water intake, we have their water out at all times. They prefer ice cubes be added in the morning, before bed at night and maybe once during the day. They both drink a lot of water.
Mom to Abby & Gizmo