When to stick a fork in it?

I've spent the past week (in between teaching English 101, Science Fiction, Beowulf and Old Norse) doing revisions on How Tradition Works. Part of this process has been reading new books suggested by my outside reviewers. Some of these have proven helpful, some less so.
My question is: when do you just say "stick a fork in it, it's done?" I finished HTW in April, revised it in August, and then got reader's reports back in December and January. But really the bulk of the reading and research was done when I was on research leave in 2001. Since then there has been a lot of important scholarship that has come out. But I can't completely re-write HTW each time I read a new book on Memes or on the 10th century. It's frustrating. For example, I just read Religion Explained by Pascal Boyer. Brilliant argument. Only tangentially related to my book, but I wonder if I should go through HTW and at least reference each time Boyer's argument might be useful or connected or (my favorite) "not incompatible" with my thesis.

Any writers out there have good rules of thumb for deciding when to stop and just include all the new scholarship in the sequel?