One per year would fix it too. It's not even that I think people should need to book at 11 months. I simply find it irritating that they are available for those not staying there. IMO, it's the opening these up for locals or "few hours drive" people to pop in for just the night that really messes up availability. It means I could easily be competing with 2-3x as many people (especially because not everyone even wants to go) vs if it was simply whoever is "already going to be there" - acknowledging of course some people will change dates. The issue is once it's opened to people without a reservation, it gets more difficult and the whole things snowballs to where we are now. (it not much different from the whole "where's the line where too many rentals are happening and
DVC should get involved" discussion, in both cases, that line is there somewhere) If it weren't open to off-site guests I don't think it would be getting as coveted which would make it easier in the first place, making it so people didn't need to shift dates, and it could be a random extra fun thing similar to EMH.
Truly, if they can open EMH to everyone at all deluxes with no restrictions and it's not feeling crowded, it's a good question why "DVC-Y AND staying in a DVC room" would be too many people.