That's not quite what I meant. I believe we have knockout mice that age much more slowly than normal mice, but many of them do not have longer lifespans, because they still get cancers.
I still don't think so. For example, you can easily increase life span of mice by ~25% by simply restricting their calorie intake. There is also the issue with the definition of "long life", which is 3 years for mice. For that to be plausible, average mutation rates should be VASTLY larger in mice than humans, which doesn't seem to be the case.
https://www.pnas.org/content/99/2/803.long