iPad backup takes hours

The time required to perform a backup will be affected by many factors.

If performing an iCloud backup, or backup to another Cloud storage, your internet connection speed will have significant impact; the slower your connection, the longer the backup will take. Large backups will obviously require more time.

If instead your are making an iTunes backup via USB, the USB specification of your computer will impact how quickly data can be transferred. Likewise, the speed that data can be transferred to storage will also influence backup performance. HDD drives tend to be slower than modern SSD drives.

This might happen if your iPad has many applications, photos, videos, songs, and more on it.