Someone commented to me that they considered knitting from their stash as "free knitting". After thinking a moment, I realized I pretty much think of it that way too. Just consider that sense of unique accomplishment you get when you knit with a yarn you purchased over a year ago. You consider yourself frugal, efficient, etc. You didn't buy anything for this project! You "used up" something you already had. The fact that this means you bought the yarn purely for the sake of buying yarn never enters into the equation. Nope. That fact just doesn't exist.
And that is what a multifaceted hobby is all about.
Aren't you glad I explained that to you?