How long does it take an iPhone to update to iOS 7?

I have an iPhone 4S, and I still have the iOS 6 software. How long will it take me to update the software? (I know it took a while when it first came out because everyone was downloading it at once, will it be the same or a shorter time now?) also, will anything get deleted? Especially the text messages? I don't want to lose my texts or photos.

Took me 3 hours. But it depends in your internet connection. If you have a faster internet then it will be lesser.

It is possible that you may lose data. So, back up the iPhone first via iTunes on a computer.

The devices that are iOS 7 compatible are:

iPhone

iPhone 5S
iPhone 5C
iPhone 5

iPhone 4S, but does not support:
Filters in Camera app
AirDrop

The link below may help you more with this.