I do the same thing. Most of the time I use it all the way until the 10% battery warning.I plug mine in every night before I go to sleep. When I wake up, it's fully charged and lasts me all day. Depending on how much I used it in a given day, it could be anywhere from 50% to 10% battery life remaining.
I put mine in the special Onkyo charging dock connected to my Onkyo surround receiver when I get home from work or where ever I've been. It stays in there unless I need to use until the next day when I leave for work or go out somewhere.
The spousal unit is a power electronics (battery) engineer/specialist. I asked him when to charge and he said, "Because of technobabble, you don't want to go any lower than 20% or maybe 10%. But you really want to avoid that because of the velociraptors. Also, try not to charge it above 90% because the the terrorists will have won."
My mind may have wondered a bit.