I'm also using a 2600k (non-overclocked). I'm going to upgrade soon though. The main reason is I want to take advantage of things like usb 3 and an m.2 ssd. I also want to get a new video card and I'm using it as an excuse to build a new computer.
My old desktop was passed down to my wife, who was previously using my 3rd most recent desktop, a Core2 Duo (E6600 I think). The 2500K/2600K still has much life left in it for many tasks.