His laptop is the 17 R4 7700HQ+16GB+1070+1440p GSync screen variant. (50-60% brightness)
That one has 99WH battery.
He asked the customer service before buying and the answer is really about 2-3 hours during full load e.g. during games .
This 2-3 hours is not an exact number, it will varies from game to game.
And the thumb rule, 50% of that what the manufacturers told you is realistic.
2-3 hours max said the customer service, my bro gets 1.5hours, this is still quite good.
All desktop replacements laptops should be like that too.