I was going to spend the day on the game as it's raining, but it's too repetetive. For every mission, there's a radio tower to climb (which reveals the map) and 1-2 enemy outposts to clear out (which prevents enemy patrols).
The game is good, don't get me wrong, but it involves spending a lot of time doing the same thing over and over, in the same environment each time.
It's a 'play an hour a day' kinda game rather than a 'blitz through in a weekend' kinda game.