Okay fourth test done. Sleeping from the home screen instead of from a book made no difference at all. I got 92.3 hours (3.8 days) of battery life. This time I did some reading as well: 4h52m of reading in total, with no battery drain during reading whatsoever. Battery drain occurred only during sleep, and then a little after waking up the Glo (either still on the home screen or in the book). One difference: the batter seemed to go all the way down to 11% instead of drop from around 42%. But then, I did some reading and it was day time instead of the 43->0% drop during the night, so it might have done that all along.
Code:
7 Mar 2013 21:38 100% home screen, sleep
8 Mar 2013 09:34 100% on, sleep 11h 56m
8 Mar 2013 22:19 78% on, left on home screen 12h 45m
8 Mar 2013 22:30 68% to epub, reading+light 0h 11m
8 Mar 2013 23:17 68% to home screen, sleep 0h 47m
9 Mar 2013 09:36 68% on, sleep 10h 19m
9 Mar 2013 11:26 66% on, open book 1h 50m
9 Mar 2013 11:27 63% reading + light 0h 1m
9 Mar 2013 11:50 63% home screen, sleep 0h 23m
9 Mar 2013 21:23 59% on, open book 9h 33m
9 Mar 2013 21:24 56% reading + light 0h 1m
9 Mar 2013 22:13 56% home screen, sleep 0h 49m
10 Mar 2013 11:19 56% on, sleep 13h 6m
10 Mar 2013 18:54 47% on, sleep 7h 35m
10 Mar 2013 20:30 43% on, reading+light 1h 36m
10 Mar 2013 22:37 43% home screen 2h 7m
10 Mar 2013 22:38 42% sleep 0h 1m
11 Mar 2013 09:43 42% on 11h 5m
11 Mar 2013 16:15 20% on 6h 32m
11 Mar 2013 16:15 17% open book 0h 0m
11 Mar 2013 16:15 13% reading + light 0h 0m
11 Mar 2013 17:01 11% home screen, sleep 0h 46m
11 Mar 2013 17:55 0% nothing 0h 54m