I have one that I pin basted about 4 years ago and did everything but the binding about a year ago and it was fine. Its companion that was done a few months prior that I started hand quilting and put away and take out to work on periodically is fine as well. That one is black and red,copper and antique gold so even if rust developed it wouldn't show!

I have a quilt that's been sitting, basted and partially hand-quilted, for about six or seven years. I've dug it back out of the closet to get back to it soon, hopefully it will be fine!

I don't think there is a time limit. On utube it even showed on quilter who spray basted 5yrs ago and it's still holding.

If I take the time to baste, pin or thread, I usually don't fold them at all and quilt them within a week or so.

I have one basted for a couple yrs. I just checked it & it looks the same as when I put it away. Still has the ugly backing fabric.