How long does it take to Back up an Iphone?

So this is the first time I pluged in my iphone 5 to back up in itunes, its been like 2 hours with the same msg Syncing Iphone (Step 2 of 5) And there's no any percentage bar… So I have no idea how long does it usually take? I need to swith off my pc already but the update is still going and no idea when it will finish…

You just have to leave it.
It will take a very long time but just be persistent or just leave your computer on!

Go to setting then go iCloud then it will say back up

Well there's the problem. If you backup often enough it would take minutes, sometimes less than 1, but the longer time between backups the longer it will take.