Rinsed yeast will keep for a little while in the fridge. I’ve used rinsed yeast that’s been in mason jars, in the fridge for up to 6 months. Here’s what I do:
http://billybrew.com/yeast-washing
I like to use the yeast within 2-3 months but have used yeast that’s been 6 months old (and older). Of course the viability goes down over time so a starter is needed, but if you use it within maybe 2-3 weeks no starter is usually needed (depending on how much yeast you need). I use to save yeast for a long time but recently started dumping it when it gets to about 6 months old. At that point I’d be spending more on making a big starter with DME then just buying a new pack of yeast.