Lets say it's January. This month its Iron Banner. Inn February its SRL. In March its Iron Banner In April its SRL. See where this is going? Now we would have two loot systems to collect and it gives us some sort of variety.
I'd rather it be weekly. 1week Iron Banner... The next SRL... The next the wolves bounties from the queen...etc. Something like that so we aren't waiting around for a month for just one week of content.