my iPad 3 constantly freezes and requires a hardboot and that now takes 10-15 minutes to reboot.

Try a System Restore. First backup your device using iTunes. Also import your photos to your computer and copy all important data if possible. Try restoring from backup first and testing it. If it does not help, you may have to restore as New and reconfigure from scratch as the backup could be corrupted. For this reason it is important to have your photos and data saved separately from the backup. Here are the steps for a Restore:

https://support.apple.com/en-us/HT201252

If the above steps do not help, you may have to have it tested at an Apple store.