With modem and WiFi on I got 5h 34min, and with both off - 7h 45min. With final battery that should translate to about 9h and 12h respectively.
This progress comes mostly due to runtime power management improvements - we don't suspend the CPU! With WiFi on, the phone was reachable and ssh-able through all this time.
@vancha Yes, the CPU can be woken up by the modem.
Our plan is to work on runtime power management to get it into good shape first, then we may consider using suspend to RAM. There is an ATF branch where it works already, but it currently breaks DRAM frequency scaling, so it's not really worth it as it is right now.