How long will this PC last?

Gotta love Cyberpower names, they sound so good .... Gamer Ultra. HA! The dam thing doesn't even have a gaming GPU in it.

You would need to add in an aftermarket GPU to game at decent res and high settings and possibly an decent power supply to. I would expect to spend at least another 250 on that system to get it gaming capable.
 
For $40 more, the following PC is a much better deal. It comes with a quad core FX-4100 and a Radeon HD 7750 graphics card. While the HD 7750 is an enormously big performance boost over the HD 6450, it is only considered at mainstream graphic card. But it's is simply the performing graphics card in the price range of $90 - $110 that works with a 300w power supply if you were to buy it separately.

http://www.newegg.com/Product/Product.aspx?Item=N82E16883227437