Airport arrival time for flight back to USA?

We're hearing mixed answers, the cab service wants us at the airport 3 hours ahead of departure but the staff at the hotel say 1 - 1.5 hours is enough.

We're leaving on Jan 1 and not sure if the cabs think it'll be a heavy travel day or if they are just too booked and don't want us to call another company.

If I can avoid twittling my thumbs for 3 hours while I could be soaking up another hour or so of sun I'd rather that.