My Sister worked in a quilt shop in the mid 70's, and bought a lot of fabric. A few years ago I bought it all from her (about 300 yards). So I have not owned it that long, but it's been in the family . . . I've used maybe 40 yards of it so far.
Personally, I have some fabric I bought back in the mid 80's that I have not used yet. I made most of the clothing for my two kids until I went back to school (about the same time they went to school). Didn't sew much for about 20 years and am back into it now. I had 2-3 boxes of fabrics that have moved around with me during this time. I finally have all my fabric unboxed and on shelves (if suitable for quilting) or totes so I know what I have.