Thought I'd join in on my shave free day and test out how far I could stretch one of the vegan soaps - WSP Amber Vanille. So went about a palm lather, went to a point where I would normally use it, and then keep going. I now know, that I don't give this vegan soap enough credit for how much water it can take and still be stable, thick and slick, without washing out too much. (next time I'll break out the proper camera and resize a bit smaller)
About 5 swishes of water past my usual point
About 15 more on top of the last one
At that point I gave up and washed it away, because I'd never spend that amount of time on a lather in the mornings anyway, but did certainly learn that by using merkur man's method, slow adding, I can push it a lot further than I previously gave credit for.