what do you do when your build is near complete

well he has cartographer boxes to get free 77s from, so he can run them blue and easy.

If you are 75 and doing 77's you'd be getting sick exp from them and wouldn't be 75 for long at all. And if you were doing them even earlier so that by lvl 75 you are bored of 77...well just quit till next league and maybe you'd find it interesting again.

My build is pretty much complete and I have solid to great gear. I can do regular and blue modded maps to 78 with ease, and many yellow modded maps. I'm squarely in the "end game" as an 87 Marauder.

But with that said, still plenty to do and gain. Why? Because I want to be invincible, plain and simple. Though I have a nice toon, I literally want to roll over EVERYTHING in my path. I'm not there yet, and perhaps, will never get there, but I will do all I can do get there. That gives me plenty of incentive to play. POE IMHO has done a good job and keeping that carrot in front of you. That carrot, is immortality. :)

Who knows, when I hit 100 and a full passive tree, perhaps I will have "won" by basically steamrolling over anything in my path. But I doubt it. And until I get there, I will continue to learn, tweak, farm and improve.