Our little friends Rattus norvegicus are like soap bubbles: full of rainbows for the brief moment they last. Who knows how human history would be different if pestiferous wild rats could live for ten years, though if they lived that long they'd probably breed less frantically, so there might not be a big difference in their numbers -- and longer generations means less enthusiastic mutation, which is one of R. norvegicus's chief defenses against us because it makes poisoning them difficult. All the rat population has to do is keep enough individuals alive to breed until the right mutation comes up to protect them from the effects of the poison. For Norways, who live maybe two years tops in the wild, and are fertile at six weeks, this generally doesn't take long. Pretty soon your rat population is surging back to full strength, fat and happy on the Warfarin-laced bait you've been setting out. Thanks for the free food!
Anyway, I don't care what effect a decagenarian rat would have on humanity, humanity can bite me -- I just want a pet rat that won't sprout tumors if someone looks at it funny. Oh, and it can fly, too. You should see them grooming each other's little wings! It's precious!