If this is a domestic flight and there are seats open in C or F then when upgrades start clearing at the 120 hour mark then there will be some E+ seats vacated by elites who move up to F. So I would keep checking seat maps and move into open E+ seats then. Even if only one seat shows available in E+ (an aisle or middle) it's probable that the middle next to it is also open and you can call and have them assign it to you after you take the open aisle/window.