From what I recall, Caspian mentioned in Discord that the Aristocracy+ packages would be going away just before Domain selection (that's when everyone will pick their settlements, so it makes sense not to offer packages that include land after all the land has been "given away").
He did say that we would have fair warning before they left, but how much time that actually means he didn't specify.
Given we are not far from map selection now, and domain selection is supposedly "soon" after that, I would wager you have 3-6 months left on them.