well, we had a debate about this topic the other day with a few nail artists, and we all use some brush cleaner for these emergency situations, when in training you're doing something and someone asks something, you stop and leave your brush "inattented" and BAM. and obviously it's everytime our fav...
so out of the numerous brushes I have, almost all of them had a BC shower already... we don't leave them soaking for hours, we have a special thingy that holds it so the tip of the hair doesn't lean... and I swaer they're all fine and still working, and some have more than a year with me...
but obviously, not all the brushes will survive it (this was another's debate topic), not all the brushes are equal to this treatment, you then know which are the good brushes and which aren't. the "cheap" ones I had when I started all died...
as for having a brush per monomere, that's what I do, along with having brushes for glitters, brushes for nail art detailing, etc. you may think you can do all with one, but why complicating your life?