There could be plenty of reasons while your iPhone takes too much time for backup. The users who are doing the first-time backup, this will be a time taking process. The issues never persist in future backups. Besides, the presence of a large number of pictures in the camera roll of your iPhone increases the time of backing it up. They consume a lot of storage space. Voice memos, large video files, and messaging apps when backed up together, they can eat a lot of time. Remove unnecessary files from the iCloud or delete some files from your phone’s storage.