Uh, it's 3 years in Japan and 2 and a half years in US/EU. Gen V doesn't end until Gen VI begins.
You need to remember it ended the moment B/W2 hit the market.
It is our shortest gem yet though.
No, you're wrong. By your logic Gen 4 was only 3 years long, but anyone here will tell you it's a 4 year gen. It doesn't end when the last games come out. Black 2 and White 2 may be the last main games, but the anime, movies, merchandise and spin-offs are all for gen 5, not gen 6.