I will have an 8:45 am flight to London from the Shannon airport on a Thursday morning in early September. Is it crazy to stay in Doolin the night before? I would, of course, love to be closer, but really want to spend a night around the music in Doolin. How long would the drive take?

You can have the music (Cruise's Restaurant & Pub) and be much closer if you stay in Ennis. I booked a taxi the day before in Ennis for a 5:30 AM airport run; and he was at the door of the Hotel at that time. It took about 25-30 min to Shannon at that hour of the early AM. Doolin would probably be twice that.
BTW
The upper level Cafeteria at Shannon opens at 7:00 AM. I told the people at the Queen's Hotel I wouldn't be having breakfast and they knocked 5-Euro off my bill.

You don't have the same security at check-in as if you were flying to the U.S.

I would allow AT LEAST one and a half hours for the drive from Doolin to Shannon. ADD in arriving 1-2 hours early to return the rental car, etcetera and you would be looking at departing Dooling between 5:30 and 6 AM.

Agree with Ned -- Ennis will likely be the better choice - in September - for music AND convenience. It's about a 30 minute drive, so you could 'Sleep In' a BIT longer.

Bob

Thanks. Just what I needed to know. I am assuming we do not need to be there 2 hours early, but that 7 am or so for an 8:45 flight would be sufficient. Am also assuming, maybe incorrectly, that September will be after the really high tourist vacation seasons...

I have stayed in Ennis for my final night and also in Doolin. We had an early flight and it was no problem driving to Shannon from Doolin. I would do it again and we went in February when it was still dark outside. Shannon is such a small airport that check in really takes no time at all. Ennis was okay...but I much prefer Doolin. If you get to the airport by 7:30 you would be fine. If you stay in Doolin try Nellie Dee's B&B. We just went to Ireland again this April and loved it. Have a great time in Ireland.