How long do fortresses stay weakened

Well after a few more hours into Far Cry 4 I found out, that you only get rewarded for repairing armored trucks (the ones you have to protect while the golden path solidier is driving to the destination). So I'd suggest that you always repair those trucks after delivering them - get those extra bucks. As far as repairing other things go, a repair sign only pops up when a vehicle is heavily damaged.

Edit: Sometimes you'll see a civilian vehicle standing alongside the road with a smoking hood. When you spot one of those, you can repair their vehicle and they'll give you some money in exchange.

There are 4 endings:

• After dining with Pagan in the very beginning, wait for him to return back to the table (around 15 min), and this will trigger the 1st ending

• At the end of the game, you can choose to kill Pagan, this will trigger the 2nd ending

• At the end of the game, you can choose not to kill Pagan, and go with Pagan to scatter your mother's ashes. Pagan will fly away on his helicopter, and you do not shoot the helicopter down.
• At the end of the game, you can choose not to kill Pagan, and go with Pagan to scatter your mother's ashes. Pagan will fly away on his helicopter, and if you have an RPG or Grenade Launcher with you you can take out his helicopter, which creates a mini area, where you can loot his body (amongst the helicopter wreckage)

There are 2 secret endings, that happen no matter what and vary depending on the ally you sided with (Amita/Sabal):

Sabal

• Travel to Jalendu Temple, the same temple you were tasked with destroying or saving in a previous Golden Path mission, to find Sabal’s scene.

• Here you’ll witness Sabal putting subjects to death for turning against Kyrat’s national religion. This cutscene only appears if you side with Sabal and make him leader of the Golden Path.

Amita

• Travel to the town of Tirtha to see how Amita gets labor. This scene can only be found if you make Amita the leader of the Golden Path by destroying Jalendu Temple.

• Golden Path soldiers are rounding up children for slave labor in her opium farms.