Microsoft's Xbox Live Rewards scheme is offering free Microsoft Points to those who spend time with Halo 4's multiplayer - that is, pretty much everyone on Xbox Live right now.
Assuming you're enlisted in Xbox Live Rewards already, you have until November 30 to take advantage of the Combat Tour offer.
Those who put in over 35 hours in Halo 4's multiplayer before then will net 100 MS Points; over 70 hours scores you 300 MS Points; and a whopping 140 hours brings in 600 MS Points.
There's also a promotion on which will refund some points you spend on the game, again only for Xbox Live Rewards members. Spending 1500 MS Points on Halo content will refund 100 MS Points, while a spend of will earn back 200 MS Points.
Mix it up a little, if you like; putting in over 35 hours and spending 3000 points will score you 800 MS Points.