I measure when I bring it home, and majority of the time it is what I asked for, save for a local store that short-changes because they really should be using a ruler and rotary cutter. But that story has been beaten to death. After I wash the fabric, I measure again and place a small label with size on the fabric so I know when planning a quilt, what I am dealing with. I remember getting 60" wide fabric many many years ago. Since most of the fabric now averages about 42", I too don't plan anything for more than 40". Just went through some stash yesterday and could not believe the differences in selvages. Some 1/4", others averaged just shy of 1/2", and one was even 7/8" inch on one edge, the other edge was 1/2". Odd.