Nitpick: years gained is rather optimistic for mice. Months is more likely.
With Googling you seem to be right that mouse lifespan extensions seem to be reported in months. I personally would still prefer to report results that are less than a year in years. Months have the annoying habit of having either 19, 28, 29, 30 or 31 days in length.
In at least one paper I've seen on this subject, month was fixed as a 30 day period. But even without that, as an approximation, months work pretty well for reporting the rough increase. The difference between 29 and 31 days will get swamped in the error margin for anything less than six months or so. And since most months are 30 or 31, and many alternate, in practice, this will be very close to 30.5 days, so the difference will be negligible.
This seems like an advance in understanding, even if it doesn't lead directly to a treatment.
News stories:
http://www.theguardian.com/science/2013/dec/20/anti-ageing-human-trials?CMP=EMCNEWEML6619I2
http://www.bbc.co.uk/news/health-25445748
Abstract of the paper, actual paper behind a paywall:
http://www.cell.com/retrieve/pii/S0092867413015213?cc=y
Relatively solid stories like this help raise my estimate that significant life extension is possible in our lifetimes. The likelihood seems to be that it won't be a "magic pill" but a combination of therapies.
If nothing else, it's another reason to eat healthy and stay in shape.