Micro/Nano Gas Turbine Engines easily surpass batteries over 1h, but are not cheap or easy to use. And, if you only need 10 minutes at a time for testing then batteries are significantly lower weight.
EX: Wren's MW44i 46 oz (1320g) and produces almost 7 hp or ~5kw.
Above a certain size, it's simply more realistic to use variable pitch rotors that don't rely on speed changes to maintain stability, at which point the traditional helicopter design becomes more efficient.
Increasing the weight increases the engine & prop size, which increases your energy needs.
EDIT: From the few multirotors with a gas engine that I've seen, the right combination of weight - maneuverability sweet spot appears to be around the 750mm size - around 2 feet in diameter. They also tend to have good flight times, but still in the sub-one hour range. Again due to weight.