I used to do that, then I released how many pieces of software I have installed, and tweaked and adjusted to my preferences. Usually there is little benefit to an upgrade so I just leave as is (or use a rolling release Linux distro).

I get similar memory leaks with WindowServer on a brand new macbook pro. The damn process is eating 4gb of ram sometimes...

I did a fresh install from a seemingly healthy, semi-recent MBP and Yosemite's WindowServer seemed to begin a slow strangulation on my machine.

Solved it by buying a top-of-the-line machine, which I'm sure Apple is loving.

I discovered a weird interaction between f.lux and fullscreen gaming. They seemed to fight about which gamma etc to use.

It was nothing you could see, and other than a jerky in-game mouse you did not notice it. And after an hour of playing, dying cmd+tabbing out to Safari to surf while waiting for respawn, WindowServer core dumped, logging out all users in an instant.

This is fixed in 10.10.3. The jerky mouse pointer problem still remains. I don't use f.lux anymore.

Gotta be a hardware issue of some variety. I'm running Yosemite on a MBPro Retina mid-2012 with zero issues at all.

Hmmmm, possibly my slow-as-could-be hard drive. The SSD in my newer machine really does make a HUGE difference, to speak obviously ;)

I have the feeling my old machine is using a bit of VRAM when WindowServer starts getting too heavy.