Tablets have large screens, so they have higher battery consumption than mobile phones, when using the same features. Display has quite large battery consumption in general. Battery with capacity 5000 mAh may be considered as good enough for a mobile phone, but not for tablet.
If you buy a tablet with 7000 mAh battery, it should last at least 6 - 8 hours on average usage. To use a tablet for 10 - 12 hours without charging, you should buy one with battery capacity around 10 000 mAh.