For wikis devoted to technical discussion, it can be beneficial to have permanent KeepDays?. I've often found it very handy that my CVS for code I've written is completely unpruned; it does happen that I want something that was discussed or written five years back, and then deleted or ignored until the present.
So I can set KeepDays? to a big giant number, but I'd rather have a configuration option that just meant "forever".
It's way way easier to just set KeepDays? to = 365 * 100.