Ours is a small, low-volume shop where I wear most of the hats, including design. We've only recently grown to the point where I've started to outsource when I'm maxed out. For me, it's a shift of mentality - from "a penny saved is a penny earned" (=I'll do it even though I'm slow at it) TO time saved is money earned (=outsource to someone who can do it faster, so that I can do something more profitable). Right now, outsourcing only makes sense when my schedule is full; if I've got the time, I might as well do it & keep the money.
I'll add that I'm curious how people found/find their outside artists. Finding & working with an artist, + how to know what fair pricing is - that's something I haven't wandered across many articles/threads/how to's on. I just work with a graphic designer I know personally; he's good, but I wish he knew something about textile printing without me having to teach him!