Past 5h, irrelevant to me. 5h is the longest continuous amount of time I can work on a hard problem, at least without the modern amenities that come with DC power, like a cold drink, etc.
After that, I get a break, and so does my laptop, for 30 min to 1h during which we both recharge our batteries.
That's far less sexy than a laptop with 24h+ of battery life, but I like to carry my laptop in a small bag, so the AC adapter doesn't intrude much.
Actually, I have 2 bags: both feature an AC adapter. I carry either the "big" bag with a regular Lenovo keyboard (I like it) and a 65W GaN adapter from Aohi (a cube about 2cm per side, that's not your grandpa power brick) or a flat 20W adapter (shaped like a 6mm thick credit card, with foldable blades) that's perfect for my Lenovo that barely sucks 10W (I measured).