Interesting- starting Tuesday Oct. 6 you can request the upgrade when you book your flights... then the upgrades clear automatically at your upgrade window ( remains 14 days for Se in NA and 7 days for SE for Intl.) or later if no upgrade seats are available at the upgrade window.
At upgrade window, upgrades clear by fare first (Lat and Prem Econ. Flexible) then by status (For same status members Priority is done by fare).