My work laptop doesn't have a discrete GPU; I bought it explicitly to get better battery life (I really like the gaming laptop for its 120Hz screen and other specs, but the battery life made it a no-go). It gets around 4-5 hours, which is good enough for me, but I'm sure it would get better battery life on Windows.
How did you get better battery life on the gaming laptop, if you don't mind my asking? It uses a NVIDIA GPU.