Thanks for the advice. I feel a bit foolish as if I'd waited a bit longer I wouldn't have posted.
I'm happy to say that it has now gone down to 3/4 so I know it's working - just pleasantly surprised at how long it goes before depleting. The Iliads went to 3/4 almost immediately, so I was expecting a similar thing on the 505.
I'll continue to just use the slider to turn it 'off' unless I know I'm not going to be reading for a while. Another bonus - the Iliad always takes a long time to wake up.
Lyn