I've done a couple of brews recently where I've dumped fresh wort onto the yeast cake from a batch I've just bottled. (This was two different yeast cakes, not reusing the same one several times) So far no issues that I'm aware of... But I'm sure I read, or heard something on a podcast, recently suggesting that it's ok to reuse a yeast cake but you should only use half the yeast cake. The reasoning is you've got old and dead yeast cells in there - by using less yeast cake I guess you've still got plenty of viable cells in there but by starting with fewer cells you're encouraging them to grow and multiply. (On that basis I'd have thought even a third or even a quarter yeast cake could be plenty to start with, depending a bit on ale Vs. lager yeast, your OG etc.) Anyone got any thoughts on this?