One of the less appealing aspects of the twice-yearly Windows 10 feature updates is that they're slow to install and, for most of the installation process, your PC is out of commission, doing nothing more than displaying a progress indicator.
Thanks to a new upgrade process, the next update—expected to be released in April—should result in substantially less downtime. The install process is split into two portions: the "online" portion, during which your PC is still usable, and the "offline" portion after the reboot, during which your PC is a spinning percentage counter.
Microsoft estimates that the Creators Update, released almost a year ago, would take about 82 minutes on average during the offline phase. Improvements made in the Fall Creators Update cut that to about 51 minutes, and the next update (which still hasn't actually been blessed with an official name) will cut this further still, to just 30 minutes.