Sorry. I wish I could help you but, alas I am having issues with my girl too.
She is going to be 8 months old on the 12th. She does let me know when she has to go out but.......I take her out and there are times she just doesn't do anything. Then it's back in the house we go only to take her out a little while later. Another issue I am still having is that even though I take her out right before I go to bed, she messes in her crate during the night. She doesn't eat late either. She does not bark or whine to let me know she wants to go out during the night. She just goes in her crate.
I would think at her age she should be able to hold it for at least 6 hours.
I too have to watch that my little one doesn't run out the door. I have a lot of work to do with her yet!
Sorry I couldn't help you with your little one.