When I started out, I just bought what was pretty. I look at some of the older stuff and wonder "What was I thinking?". Some of it is very thin. A few years ago I had made a quilt for my dog. (That's him on the left laying on it). After it had been washed just about 7 times one fabric was pulling away and shredding.
Now, I only buy the good stuff. I want my quilts to last. I check to see if it is soft and has good weight.