Depends what hardware you are installing the OS onto. On my NVMe/SSD equipped desktop (and using custom settings) I'm through in under seven minutes. If I used only default settings it would take even less. On a system with a slow HDD it can easily take half an hour or more.
Installing the OS is usually the simple and fast part though. Making sure all your data is backed up beforehand, configuring Windows and installing all the software you use, possibly getting newer versions of software you already use to better support the new OS, etc... those are the real time sinks.