After purchasing membership for one month, existing members should be able to purchase the following months of their tenure with gold, rather than having to spend irl cash.
As a paying member myself, I have to spend my hard earned money every month to continue to play in the later worlds with the added benefits. Players, however, are able to earn gold through playing the game naturally. This would offer an incentive to continue playing the game, in order to get the next month of membership.
This would only be offered to players who have an active membership and players that have already completed the main quest line.