Thank you both very much. Departure time is 6:40 pm on a Thursday in June. Local flight to Athens on Aegean in business class. No checked bags. Might make more sense to wait in my hotel lobby? The only uncertainty is how long it takes to clear security. This looks like the kind of airport where you'd want to arrive just 45 minutes before the flight, but if security takes over an hour, you'll be stuck there for much longer!
I would plan to arrive by 17:00 or 17:15.