It all depends ... since you already are exhausted, you won't feel much like getting up early int he AM to get a flight -- you'd have to be there 1 hour ahead, and even the 7:10 AM flight to Santorini is €106 ... and you'd have to be there at 6 am or so. The alternative: if you can just Grit your teeth, get a snack in the airport and hang on a bit longer: there's an Aegean flight (€96) at 22:35, arrives 23: 20. If you arrange for a car to meet you, you can be at a hotel at midnight, and then CRASH. It doesn't even have to be your "exquisite hotel" .... just one that's convenient. Sleep in, have a leisurely breakfast, check out and THEN go to your upscale "dream hotel".
Staying near airport doesn't get you to bed any earlier... you'd have to rise at 5 am to even get that €106 flight. The best alternative I know is AVRA HOTEL , about 20-25 minutes away from Airport in Rafina... and if you request at time of booking they have FREE shuttle bus 24/7 . Airport crowds will be thin at 20:45, so you could be out of the airport by maybe 21:30, shuttle to Avra by 22:00, check in, have quick snack (They have cafe on premises) & be in bed by midnight. However the first option lets you sleep late, & awaken on a lovely island... so that would be my choice.