Why is my icloud backup taking so long?
iCloud backups the following:


Photos and videos in the Camera Roll
Device settings (for example: Phone Favorites, Wallpaper, and Mail, Contacts, Calendar accounts)
App data
Home screen and app organization
Messages (iMessage, SMS, and MMS)
Ringtones
Visual Voicemails


It might be due to your app data size and also if this is the first time backing up then it will take a bit longer. Have a look at this link, it will explain why else it might  take longer.