It's allegedly only for the current batch of birds.
I can imagine it can be a bit of a nightmare for those used to raiding on a whim (like in a big city), but for our environment, where raids generally have to be planned for them to succeed, the current system actually works quite well.
As soon as the boss is known (which is nice and short), we start the planning process on social media (Discord and Facebook) and the extended second-stage gives ample time to arrange groups, sometimes even multiple ones for the same raid.
Perhaps there's a middle ground. Would a 30 minute egg be better for your circumstances?