One of my favorite paintings is an oil I did many years ago.  Originally it was painted on a canvas panel.  For some reason, I felt the canvas would be better off the cardboard panel, so I removed it.  And then got distracted and the canvas was lying flat with some derivative pieces of it for a few months.

Much to my horror, something had been placed on it with weight and there were suddenly two large areas with removal of paint, and a crack where it had become folded.  So much for the idea of flexible oils.  I bought it some stretcher strips and re-mounted it.  It has been a couple of months.  It has flattened out, but the cracks are still visible. I have just repaired the two areas of paint removal.  Lesson learned (that I already knew) paint them and keep them as if its forever to avoid damage.

"The Yellow Flower" No. 368 painted in 1999, Winsor and Newton Artist's Oil Colors
(c) laeom

I haven't decided yet what to do about the cracks - filling them in carefully will still leave a bump. This painting and I have been best friends for many years.  The photo doesn't do it justice.