A month is fair. Especially when a tie breaker carries in to the following month. Doesn't make much sense for the same person to be able to participate in that month.
I also think ROTY should be changed as well. The main ROTY category should only be the people who have won ROTM during the year. That should make things interesting. The other sub categories can remain like they are. Just my thoughts. Might give more of a reason to participate in ROTM. A lot of people just come around for ROTY and bounce.