I find that I get about 5 hours with that particular kit.
Try buying some rechargeable 9 Volt batteries (these have lastested literally for years - having kept recharging them).
Also, you can actually fit 2 x 9V batteries in the battery box. (a bit of soldering and a extra lead and now you have approx 10hrs).
I also have 2 boxes, so one is always charged.
If you want to go all out, there is an adapter you can hard wire to the aircraft.
Just some options. Better than no ANR at all.
800