My 18-hour laptop is more like 8-10 hours of real work usage, which is still fantastic compared to the 2-3 hours I would get at similar tasks 6-7 years ago.
Another big change is improvements to sleep and standby time. I can use half the battery, close the lid, and be reasonably confident that the other half will be ready and waiting the next time I need it.
EVs may actually be an apt comparison, where an EPA rating of 300 miles is more likely to give you 240 miles at highway speeds, or 150-200mi between charging stops since the optimal charge speeds fall off above a 70% charge.