If M is the number of months then (since you can't have a fraction of a subscriber) you will be in steady state when Y * X^(M - 1) < 1 so once M > 1 - (ln Y

If M is the number of months then (since you can't have a fraction of a subscriber) you will be in steady state when Y * X^(M - 1) < 1 so once M > 1 - (ln Y / ln X)