Also, where will you be coming FROM ? Knowing that could allow you to route through some of your desired location along the way, simplifying your choice.
Another consideration is to how you wish to spend your final night -- out and about, in the pubs until late, or a quiet, early night to 'rest up'?
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Bob
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We will be coming from Connemara area, staying in Clifden, then to Killary Harbor, where we hope to take the fiord boat trip.
Our flight is at 12 Noon, so I believe we need to be at the airport by 8 AM ?
We'd like to take in a pub our last night.
Your noon flight only requires 3 hours not 4. We once turned in the car the night before a flight and stayed at the Park Inn Shannon and we felt stuck without any last night activity. If you turn in the car the night before it probably won't save a days rental because it depends when you picked up the car on arrival. If you picked it up for example at 9am on arrival you have until 9am on departure day to turn it in. If you are renting from Dooley, you have another hour grace period. I would check with your rental company to see if turning in the car the night before would save a days rental or not.
Ennis is only 45 minutes from Shannon and would be a great last night. If you stayed two nights in Ennis you could do the Cliffs from Doolin, Bunratty and the the Burren from there.
Ennis makes a good central base and since your flight is not till noon you have time to drive to the airport from there. Just give yourself time to return the car. Three hours before flight time is optimal. I like staying where I can for multiple nights. Unless you want to do the banquet or ceilli at Bunratty, Ennis might be the best bet.