I've been hand quilting about 30 yrs. Here's my various ways to end. I usually end by tying a knot close to my last stitch and pop it through, not by pulling straight through to the back, but by running the needle sideways between the layers before exiting, so I have about a 1/2 in. tail buried along with the knot. (Of course I snip the thread right where it exits the quilt.) But if my ending thread is too short to tie a knot in, I take a backstitch and then run the needle between the layers before exiting, so that about 1/2 in. or more of thread tail is buried between the layers. Sometimes I will do a backstitch or two duplicating my last two stitches, so it doesn't show as a back stitch and then run the tail between the layers of the quilt. Sometimes my thread is just too short to do anything with, then I simply slip my needle between the layers as far as it will reach before exiting and leave a long tail of thread between the layers. I've never had problems with any of these ways coming unsewn after it is quilted. The main goal is no knots or thread tails on the surface.