Following up on the XCom Time Limit Issue..

There are mods out there in the Steam Workshop that will allow you to easily expand the time limit for missions, or remove them entirely. If that’s an issue for you, then go ahead and download them. There are also three mods by the Long War team that add a new unit, a new class of weapons (Submachine Guns), and a new type of XCom unit (Leaders).

You can see them all at the Steam Workshop page.