I use the 500ml to make a 1500ml starter, and pour off 500 to save for next starter, use the 1litre for the batch. And I have been continuing that process now for 4-5 or batches. I do not wash from the fermenter. I know I could, but I have had good success the way I have been doing it, and I tried washing once and I was not too successful.
I propogated this yeast from 2 heady topper cans in early november of 2016, so about 4 months ago. I have been using it every 6 weeks or so in a batch, but I am calling gen 4 or 5 because when I first got it from the cans, I stepped it up over the course of 4 starters, going from a .025, to a .030, .035, .040 in succession after cold crash and decant, about 2 weeks time, until I was getting a real nice ferm and healthy looking yeast cake. I brew NEIPAs with it, and I am using it in lower OG in the .055 range. Ferm usually starts within 8 hours, and mostly done in 48 - Completely finished in 4 days.
I have read that using this type of yeast from heady can usually gets the best around batch 6, and starts to fall off after 10 i think. I figured I would just have to keep using it, until I notice any off flavors or low attenuation. If that happens then I will just get some more heady and do it all over again.