How long does it typically take to prepare update for iOS 15 on iPhone X

Hello gdangelo1612,

Thanks for using the Apple Support Communities. We understand that you have questions regarding how long the iOS 15 update may take. This is actually not something we could answer, since it's going to depend on several factors. Those factors will include your network speed, size of the download, device processing, etc.

If you find the installation is taking longer than you might expect it should, then you can try the suggestions provided here:

If your iPhone, iPad or iPod touch won’t update

Best regards.

My personal experience is that it can take 30 minutes or longer to "prepare" the update. The download and the actual installation usually only take a few minutes, but that prep can be pretty lengthy.