That strongly depends on what you expect from it, and what the industry comes up with in the next few years.
Do you intend to do minor upgrades at some point? If so, you would want to upgrade the GPU in about 3-4 years. Otherwise, you'll just have to turn your settings down about then.
You could probably get 4-6 years out of the CPU. Once you decide to upgrade the CPU, you probably want to start a new build.
You'll want to get an SSD to boot from. Depending on what you get and how you use it, it'll last from 5 to 10 years.
That said, the PSU you have is liable to take the entire thing out in a matter of months if you're unlucky. If you're lucky, it may last 2 years and won't destroy the computer when it goes.