I bought the annual subscription last summer. The most recent update I've gotten was in September or October, and even then, the only thing new was some small document that wasn't of any interest to me.
Buying the annual subscription isn't worth it. JBoss rarely updates their stuff, and they don't care about the people who buy the documentation. Just look through this forum and you'll see a staggering number of posts from people dissatisfied with the documentation. You'll also see that all those posts go unreplied by the JBoss group. There's no denying that the documentation is good, you'll find most of what you need in it, but the subscription just isn't worth it. I highly recommend you just go for the one time documentation deal.