Got a pixel 9a too, but the battery life, at least for now, isn't great at all. It lasts at most 1 day, on wifi, sim in 4g mode and 6 background apps which just check for notifications. Also AOD is enabled but I use my phone at most 30 minutes a day. Though, it has to be considered that the phone still isn't on the main branch, so this problem might be solved by the time the device "joins" the main branch