2 weeks ago
30min only if you win all the battles and you don't bother improving the vehicle (or don't give much thought about it). Even then it may be a little short. Games often take 2min, and they can't exceed 3min (after 3min, the game ends, and the winner is the leading team). I wasn't looking how long my first games took, but when I started looking, games took at best 1min50s.
Anyway, let's say 2min per game. 2×15=30min already. Take into account the time it takes between each game, you can add an easy 30s to 1min per game (depending on how long you have to wait at the time you play). There are parts to add to improve your vehicle, and increase chances of winning. Knowing that if you're a good addition to the team, you can easily get above 70-80% wins, but if you're not, you're most likely to get around 50% wins (there are always as much players on any team, so if you have to rely on others to win, you'll lose when they are on the opposite team).
And if you're a good addition to the team... Nice. But that's a team game. Even if you kill everybody else, teammates will have been helpful for AT LEAST one thing : Taking damages themselves, meaning that's less damage you took yourself. So you kept your wheels and weapons. You can be the best player in the world, if you lost your weapons, you won't destroy anybody, and if you lost your wheels, you will neither hinder enemies nor capture the enemy base (while you become an easy target, since you're a still target).
So yeah, I'd say 1 hour would be more accurate if you're at least an okay addition to the team, or you're lucky. Although it it, of course, possible to take less time. Nevertheless, as @WolfyMaster said, that's really not much time spent for the SG it gives.