my steps since then have been something like this (and this is purely anecdata / by-feel)
- only hibernate on battery for a couple hours at a time (e.g. airplane) and only if 50%+ battery. overnight hibernation only on charger.
- when powering off the device, make sure it is truly off before closing it! sometimes I found it will hibernate instead, if you close it right after telling it power-off...!
- stick at the kindle v220.127.116.115 recommended by songoffire. do not upgrade past that, ever.
- don't install or use any version of google books :-(
- don't go randomly installing new interesting apps, stick with those that have always worked. do lots of research if a new app is to be installed, and be prepared to re-flash (and to suspect the newly installed app for causing it!)
- don't upgrade apps if they have been working fine (unless there are important new features or bugfixes)*
- don't upgrade apps without thoroughly reading changelogs (esp. to see if there are e.g. added or upgraded graphics/ui modes)
* apps like gapps, k9mail, terminal/ssh programs, Estrongs stuff etc. - I tend to trust for upgrades, since they aren't really graphically oriented, and it's only graphics-API-intensive apps that have seemed to freeze/crash my PE.
also: jdm001, now your experience makes me wonder even more about how safe battery hibernation is. thinking about what ivanjt said, maybe before hibernation I should try to remember to turn off all radio hardware and kill *basically everything* with ES task manager.
last year, I think there was once or twice I had to re-flash because of one strange behavior or another. at that time I never used kindle or google books, but I feel like I probably did let the battery die while hibernating...