I buy mostly for my stash, and then pull out fabric depending on the quilt I'm wanting to make.
So it's rare that I even have something specific in mind when I'm buying fabric, so no - the end product has very little affect on my buying decisions.
I also buy fabric where I find it, thrift, garage sales, online, LQS local and while I'm traveling, and warehouse places like SR Harris or Marshalls.
I have about 10 years until retirement, my kids are both far enough along to need no financial support. So I'm at the point in life I have the most disposable income ever and am enjoying buying fabric for the joy of buying it. I know this won't last, but I hope to have a huge stash by that time.