I’d do as Petko suggests. Each month you will be moving the robots that you had running on demo from the previous month.
Then you could put the new months robots that he has updated on a second demo account and when they have been demo trading for a month you can switch to moving the robots form that account.
Essentially have two demo accounts and alternate between the two each month for copying EAs from. Does that make sense?
You are only using 1 month results maximum to select your EAs so there is no need for running EAs for any longer on a demo account.
Hope that makes sense and sounds like a simple plan ;-)