As someone who has to use a laptop for work, I keep my laptop plugged in 8 hours or more a day, 7 days a week. The laptop's battery during these days would discharge and charge, slowly degrading the battery because only the last ~ 20% would be charged and discharged …
85% after 2.5 years is not good. My car battery has guarante of 80% capacity after 6 years. 20% of range is a significant difference so I take car of my battery and don't charge it above 80% if not needed. It's the same with laptops. Current models can easily last 5-10 years but having only 50% of capacity after that time would be a problem. Sure, if you're intending to throw it out after 3 years it doesn't really matter but if you want to use it for as long as possible you definitely should take care of the battery. It's pretty much the only part that degrades (except maybe keyboard).
85% after 2.5 years is not good. My car battery has guarante of 80% capacity after 6 years. 20% of range is a significant difference so I take car of my battery and don't charge it above 80% if not needed. It's the same with laptops. Current models can easily last 5-10 years but having only 50% of capacity after that time would be a problem. Sure, if you're intending to throw it out after 3 years it doesn't really matter but if you want to use it for as long as possible you definitely should take care of the battery. It's pretty much the only part that degrades (except maybe keyboard).