I think that BoB, based on popularity and requests, is a scenario that will probably run once every 2-3 years. (Some folks would like it to be an annual event, which could happen if we run a lot more scenarios per year, but is too often when we are at 3-4/year.)
My feeling is that, for scenarios, we should run at least 3-4 per year. (More would be better, but let's make sure we can achieve 3-4/year and go from there.) Rather than have N/year of new designs, I'd rather have N+M/year, where N are new and M are designs that ran before. Also, there are definitely ones from the past (even other than Battle of Britain) that I, as a player, want to play in again.