2 things that help:

Offline mode. As pointed out, the connection box will come up, and scan, and scan, and scan, and scan, and .... This seems to happen only when it sees an access point; I had mine set on five minute update, and watched it on an hour-long drive. Whenever the box came up, there was some wifi connection I had just driven by. Also, for over a half hour, in a rather rural area (I know of 5 APs in that half-hour stretch), it didn't come up. But in any case, if it sees a connection, and doesn't hold its current connection, it will drain your battery. (It may, in some cases, come up with no wifi anywhere close; but I haven't observed that characteristic. I use modest, but not the RSS reader.) So, offline mode.

Letting the media-scouring daemon (metalayer-crawler) loose on lots of data. Those 2 SDHC cards, do they have stuff on them? If so, is metalayer permitted to crawl them? If so, it is eating your battery... Disable it, or restrict it to the portions of your device where media might actually show up.

And one thing that might help with your online/offline mode troubles. Run a poor-man's cron (looping script that checks the time) and have it switch to online at 18:00, or something. If you want further help on this idea, I'd be glad to help out, but it probably doesn't belong in this thread. We could start a new thread for that, with the aim of coming up with a wiki page...