I wash and use yeast all the time. Actually if I'm not mistaken it's rinsing yeast since I don't use an acid solution. I just use sanitized water. I store the yeast in canning jars, just like the aforementioned sticky on washing shows.
I've pitched yeast that I've rinsed 6 weeks prior and had great results. Usually if the rinsed yeast is older than 3 weeks I'll make a starter from it. (Age based on rinse date. It may have been sleeping in the primary for several weeks prior to that.)
BTW, when I first started rinsing yeast I worried about infections. I made streak plates from the trub of a half dozen different batches. Only healthy yeast grew on the plates. I suppose it depends on sanitation, and perhaps luck. I've never had an infection from using yeast rinsed from a cake. I worry more about petite mutants more than infections now.
One thing I've noticed is that subsequent generations of yeast can act differently. For instance, I recently re-pitched some WLP002. The second batches didn't look like the first. Yeast in the original batch looked like curdled milk when roused. The next batches (two so far) didn't have that look. They still cleared nicely. They attentuated better, too, although that could be from other factors.