I buy fabrics for many different reasons. Here's my rules:
If I have a specific project in mind, I buy it.
If I can't take my eyes off of it, I buy it.
If it's on sale, I buy it.
If I want it, I buy it.
If it's black, white, some other color or a mixture of colors, I buy it.
Hey, rules are the guidelines by which we live. These are mine and I'm happy with them.