I use 1Password on everything: Mac, PC, iPhone, iPad, etc. On every device besides the iPad, I have to enter the master password a reasonable amount of time: after each reboot, after a day, etc. I count on the device security to protect access. It works as the preference choices indicate. Because these interplay with the device security, I'm able to use an obscenely long and complex master password--good times!
On my iPad, however, I'm having the opposite experience. I've loosened the requirements as far as the preferences allow, and yet I'm still being constantly--several times an hour!--prompted for the entire master password. Which is downright painful to enter on a iPad It is even more painful to enter on the iPhone, but I only have to enter it after rebooting the phone or a multi-day period. Which I can handle. But to give you an idea of the iPad experience:
Power on the device (after recharging it) and get prompted to enter the master password. Open up an app, tap in the password field, tap the "Passwords" prompt and get the password filled. Perfect.
A few minutes later, switch to a new app. Tap in the password field... must enter the entire long master password again. Note that the iPad was in use during this entire period, and never locked.
Put the iPad down to get some coffee. Pick it up again. TouchID to unlock. Try to open a website... get prompted AGAIN for the entire master password. That's 3 times in 10 minutes I could go on and on but I think you get the point.
Both the iPhone and iPad are using the latest iOS (12.3.1) and latest 1Password. One uses FaceID and the other TouchID, but there is otherwise no difference in configuration. But it's a completely different experience.
Settings on both:
Lock on exit: disabled
Auto-Lock: 1 hour
Face ID/Touch ID: enabled
1Password Version: 7.3.3
Extension Version: Not Provided
OS Version: iOS 12.3.1
Sync Type: 1Password