After the lastest update (the one that includes USSD block), my Samsung Galaxy S with android 2.3 started to have its battery drained very fast. Before the update, my battery would work for +/- 28 hrs, now it is working only for 22 hrs in the best scenario.
If I uninstall avast, it starts to work for +/- 28hrs again…
I would say it isn’t expected behaviour as one of the things in the update was meant to do was improve battery usage.
I’m only an avast mobile security user not a developer, but I haven’t seen any noticeable change in battery usage. However, I’m not what you would call a heavy user, plus at the moment the nearest cell tower to my home has been shutdown. That does cause some service hunting and that can drain the battery, given that I may have slightly battery usage as I would expect to see a loss of duration as a result of that.