I’ve got a hamster that was either born on March 11, 2010 or July 25, 2010 (I lost track which litter it’s from). It can barely see and looks like it has the mange, but still seems to hobble around without pain.
I just watched the Kids in the Hall’s series, Death Comes to Town, which has a 30-year-old cat that has been kept alive for so long that it learns to talk so it can beg to die. My hamster doesn’t seem to be hurting but I’m not sure if I could tell if he were.
I’m not sure how to humanely euthanize a hamster. A sledge hammer would do the trick but that doesn’t come across as optimal. Excessively long life spans aren’t usually a problem for hamsters.