Well, the uptime numbers keep counting without hindrance if it gets charged, so the 13 days there basically reflects the device being stable enough to run for 13 days straight on the same session.
For the record, I had to restart the device later yesterday because some leftover daemons from mcalendar (which I had deleted) were swallowing up all my resources.

As for turning it off to get in to the device later on, I wouldn't really recommend that since the power consumed from booting is enormous. Makes sense if there are some rogue processes, but turning on Offline Mode seems to solve a few problems. It would be nice if we could access that mode it gets into when "powered off" and charging (which is only two seconds away from your Maemo desktop but with all non-essential processes not running).