I'm going to buy my first mac, rMBP 15" 2015 w/ dGPU. Since, I haven't used any Mac before. I don't know about an average age of rMBP 15". Can it still work smoothly for 5-6 years? Because it is my huge investment of my career (I'm a photographer). And I want to use my computer at least 5 years before planing to buy a new one. My main purpose is processing photo by Lightroom, editing video by FinalCutPro and playing some games (like dota2, this war of mine, fifa).