^^^It's all up to you, really. You have to take a look at "how" you spend, and what you want to do away with.
For me, I love sale shopping. So, I couldn't say "Ooooonly if on sale!" because that would defeat the purpose (for me). So, whatever you decide to do should be what is right for you. If you have a swap that you do, do you HAVE to buy new yards, or do you LIKE to? Could you limit yourself to only buying for that specific thing? Or, is it POSSIBLE to shop your stash first?
It's been an interesting experience for me so far. 26 days without a fabric purchase. :D