Well Li-ion batteries are known in conventional wisdom to degrade to 70% of brand new battery life after being charged 500-1000 times. So if it was supposed to have 8 hours when new then 5-6 makes sense.
When I played around with my laptop’s power settings, the LCD screen and screen-brightness were a big power draw between 3W at dim to like 15W at max. That and all wireless functions off, if you can have an ethernet cord plugged in, no bluetooth or USB devices plugged then you can maximize your battery life. Years ago I got my laptop to host a minecraft server with screen off to like 4-5 W at idle.
E: And don’t forget if you have a backlit keyboard to turn that off.