I have the same issue with the APP for both Mac and Win.   I have the timeout set to 3 hours I have never made it beyond an hour before I get logged out.

I am ACTIVELY working - clicking save, entering products, entering POs, running reports, etc.  and I get logged out while I am working in less than an hour.  None of my time is "idle" for more than a couple of minutes.    I am constantly clicking "save" so that I do not lose any work and the system still logs me out in under an hour.

Quickbooks Online - Mac App and Windows App.