Thanks for following along with the thread, @DebbieB23.

You're correct. Three hours is the longest you can currently stay logged in to QuickBooks Online. Some important things to remember: 

• QuickBooks Online measures your time of inactivity from the last time you moved your mouse, clicked, or used your keyboard on any transaction form.
• If you are timed out, sign back into your company to continue where you left off.
• The timeout setting can only be changed by the Master Administrator, and it applies to all company users.

As my colleague has mentioned above, you can see more details about time duration in Change the timeout duration in QuickBooks Online. 

Please let me know if you have any questions or concerns. I'm always happy to lend a hand. Take care!