Is it possible to freeze yeast, after washing, so that it can be saved for a long period of time? I know most people say you can only store year for 2-3 weeks at most, but that's in the fridge.
Yes it's usually done with glycerin which you can get at your LHBS to preserve the yeast cell walls from freezing and rupturing. Most people however will make a starter first and take some small amounts of that, that way they have a lot of fresh and healthy yeast and then pitch the rest when they brew. Look up the yeast slanting threads and stickies. They go into a lot of detail about the whole process.