I wouldn't worry about voltage cut off. The GWS ESC will be fine.
The reason being that your plane simply will not be able to stay airborne at 6.5 volts or less unless it is a powered glider or something.
I've been running LiPo's in all my electrics for a while now and have never had a problem with too low of voltage. When the Lipo's fade, they'll do it fast and you'll be able to tell right away. Run your timer and you'll get a ballpark idea of how long you can fly. I think the lowest I've ever run a 2S Lipo pack down was 6.3 volts under load. That was on my MiniSpeedwing.
I caution against extended bench testing electrics. Sustained static loads are hard on your motor and ESC. If you must static bench test, keep runs as short as possible.
Once you go LiPo, you'll never go back !