What do you consider a reqgular size quilt? Do you plan to do dense quilting or minimal quilting?
5,000 yards of thread will probably get you through a minimum of 3 twin - full quilts at a medium density. That estimate includes bobbin thread.
Have fun, and if this is your first attempt, don't be discouraged. One of my first quilts was made of strips of my mothers scraps. I quilted it on my HQ16/frame - had to take all the quilting out AND 'un-sew' every seam in the quilt. That was 25 seams at 40", plus borders. So, I learned to sew straight seams the first time or pay the consequences, rip out quilting, and remake the quilt. It was worth it to me because the scraps came from my mothers stash and it made me feel close to her after she passed.