I have a stone age MP3 Player (Sandisk Sansa Clip, bought in January 2009 - Amazon never forgets) that still holds its charge to this day, for up to 8 hours even though the entire device is tiny. (I only use it rarely these days, but even so.) You can get lucky and unlucky with your batteries, larger ones do not necessarily live longer.
A dead battery in my H2O would cost me ~10€ for a new one and ~1 hour to replace (most of the time wasted on the battery glue and not wanting to break the display so you have to be super careful with that crowbar). I'm fine with that esp. since it might never come to that in the first place.
I try to avoid devices where the battery is not replaceable even if you're willing to open it up yourself. My parents have a canon camcorder with chipped battery
that is the evilest thing ever.