If you change it that often, why not use the keyboard shortcuts? 2 hours is 4. don't have predefined 15 min, though you can set a custom one to 15, then use the = as the shortcut for that.
you can also add those options to the QAT. If you add the individual items, then it would give you one click access. If you add the Period menu itself, then you can hit one keyboard shortcut like ALT+4 to dropdown the menu without any mouse (the actual number after the ALT would depend on the position of the item in the QAT)
We do not plan to add the stuff to the right click menu at this time. At least not until we add custom menus.