Running payroll is part of operating your business, and it's important that you're entering the right information to keep your books in order. I'll help ensure you're following the proper timelines.
If you're referring to how long you can remain on QuickBooks in the middle of the payroll submission process without losing progress, that will depend on your inactivity settings. If you've set up your account to keep you logged in for up to 3 hours of inactivity, then you'll have 3 hours before QuickBooks closes. If you haven't adjusted this in your advanced settings, your account will time-out after 1 hour of inactivity.