Pitching onto a yeastcake, or large amount of saved yeast is a great way to go. It definitely does help reduce the chance of infection . . . . . . with one super-important stipulation - the cake you are pitching onto, or the yeast you are saving better be from a clean beer. If it is not, then you are just pitching onto an infection. I like using mason jars to save yeast, rather than pitching into a fermenter, for this reason. You do not want to have a beer boiling away, and open up that fermenter and realize that “it ain’t quite right.” Generally, I will bottle/keg beer 5-10 days before I want to use that particular yeast. When I keg/bottle, I drink a glass of the beer from the fermenter to make sure it tastes great. If it does not taste great, I don’t save the yeast - just not worth the possibility that there was something wrong with it. If it does taste great, I split the yeast up into sanitized mason jars and put in fridge.
This saves me plenty of yeast. And, although I don’t always reuse every yeast, I bet I still cut my yeast budget in half at least.
