How far in advance of a US flight can you use preclearance at DUB?
 

While travelling through DUB in the mid-morning recently I noticed that there are announcements made for when each US flight can go through pre-clearance, I didn't think to note the timings, so am just wondering if anyone knows how far in advance of departure you can go through.

I'll be travelling to DC later this year with two friends, with Platinum AerClub status I can take 1 guest in to 51st and Green, but I'm just trying to decide whether we'll bother going in at all(and paying for a 3rd person at €35), as I'm not sure if we'll actually have much time to use it. The DC flight leaves at 12:45, and I don't know how busy it'll be/how much time we'll have between pre-clearance and boarding.

Any advice is appreciated!

I don't think there are any rules about 'when' you can go through. The announcements are just to try and manage the flow.

That's how it was the last time I went through, but on the screens two weeks ago it said to wait in the terminal, so I assumed it was something new they were doing.

This is terrible if people can only use the post-preclearance lounge or only use one lounge.

The screen announcements have always been there AFAIK.

There is no restriction on how early you can make your way through USPC (same day flight obviously).