The discoloration that I got literally developed within 20 minutes, and there is still a trace left after a year. I think that as long as there is not ongoing extravasation of blood cells, that the cellular turnover within the dermis of the skin will eventually allow the stain to resolve, at least sometimes, but it is a very slow process.
I think that I did get some results from daily warm water soaks and gentle use of a dermabrasion tool on the discolored skin.
Some guys have reported permanent bands of deeply discolored skin underneath the location a cable clamp was repeatedly applied. It is conceivable that the vacuum band applied traction to the skin which was transmitted to the skin capillaries in such a way as to damage them rendering them leaky and allowing extravasation of red cells.