The last few issues of RSA have actually been on a regular basis, and I'm going to try and maintain it, which is twice-a-year -- Spring and Fall. I could probably do three per year, but they'd be shorter in length and my Summers wouldn't be as much fun. I'll also do the free t-shirt giveaway with each issue release until the stock gets too low.
The next issue (ten) will begin a three-issue retelling of Ralph Snart's origin, you know, where he goes crazy and escapes "bitter reality" by regressing into a bizarre "fantasy otherworld" and drinks lotsa beers and parties down. I've never done a complete story, only a couple of quickie shorts -- a two-pager in FanGraphix #3 (1985 - first appearance), and a four-pager in RSA Vol 3 #5 (1989). The first issue is already written, and I plan on writing the rest of the trilogy over the Summer. And yes, Doctor Goot will snatch brains and Mister Lizard will guzzle beers (respectively) upon their return.
The upcoming issues will also start a new format -- something that will be more optimized for being viewed on digital devices. I have been doing it as a traditional printed comic with a 6-5/8" x 10-1/4" size, color covers, inside covers black & white and similar page counts. That's all comforting and familiar but has no relevance for a digital book, which has less boundaries (ie: a digital book doesn't have an inside cover). So, the new format will be closer to what I did on Volumes 6 and 7.
I'm also still working on a free book that will replace my fansite web page. Not sure when that's coming out.