It's also hard to foresee the battery duration using technical data.
One way in which you can try and estimate whether the 7.2 kwh battery of the MX 1.2 would finish an MXGP race is to consider that, ideally, it can provide an average power of 14.4 kw (19 hp) for half an hour (because 7.2/0.5=14.4). Surely a pro would use peak powers way above that number and probably less while coasting in corners and while airborne, so it is possible that it would finish but also that it would not.
Besides, in reality, there are some losses; AFAIK, mainly these two:
• when the rider opens the throttle a lot, the current flowing in the powertrain will increase and the heat loss will be higher, so part of the energy of the battery becomes useless heat. That increased current will also increase the resistance of the battery, making it less efficient.
• When the speed starts being roughly more than half the top speed, more and more current is intentionally used to create a magnetic field in the stator, the d-axis, that weakens the magnetic field of the magnets in the rotor because the motor also behaves as a generator and the higher the rpm, the more it does that. This d-axis also consumes energy from the battery. I see that some of you have increased range doing offroad with taller gearing, I guess for this reason, and i guess that in professional motocross this phenomenon would affect battery duration, too.
So then the real average power useable for half an hour would be less than those 19 hp.
One thing that can change, though, is that maybe the rules can allow electric dirtbikes to use factory batteries. At that point, that 7.2 kwh number could increase as soon as they can make a higher density battery which lasts reliably for some decent time for the team, like one racing weekend.