I've just picked up Weekly Heroic Missions on Hoth, yet that mission expires after just 12 hours. You have to complete 7 Heroic Missions to get this one, but now you have less time in which to do so. This just creates more stress and pressure for players to complete the objective before time runs out. There are 7 days in a week. Therefore, I think players should be given 7 days to complete the Weekly Heroic Missions mission on every planet.