Krusteh :
How long will it last if the minimum for me is 30 fps at any settings? Also will it last longer than the 2gb version of r9 380?
That entirely depends on what game you're talking about, and what screen resolution.
The 380 is a slightly faster gpu, but the 2gb of vram might prove start being a problem for games running at 1080p and above (although if you have an older 720p screen then it's probably enough).
What kind of games do you want to play? If you're into DOTA and LOL, then no problems....?