As Cubs said, keep the ferrule clean - bristle, ferrule (the metal bit holding the bristles), and the handle. Paint should only ever be on the business end of the bristles, never on or even Near the ferrule and, of course, not on the handle. Being human, I too use two tubs of water for cleaning while in the midst of painting. I still have a few brushes from the early seventies - the paint is wearing off of the handles but the bristles are still going! And I've demoted brushes to dry brush status when I've screwed up and gotten paint on the ferrule end of the bristles.
Also, and this is important, a key way to keep a good point on a brush is to buy a brush with very long bristles - whatever the size of the brush. Easier to avoid getting paint where it doesn't belong.