I've noticed the same thing since the July update.
I used to completely shutdown my 505 to conserve power. Since the update, I've been able to just use the power button without any noticeable lose in power.
Have made it about 1/3 of the way through Count of Monte Cristo (which is much longer than I was expecting
) and have seen my power drop to two bars. This is with just using normal shut down, and with no charge in 3 weeks.