We're traveling from Istanbul to Santorini on Aegean, changing planes in Athens. I understand that we will need to go through Border Control at Athens airport. Aegean changed the flights on us so now we have only a 1h 15m layover. How risky is this from a timing perspective?
Our alternative is to accept a much later flight to Santorini, but then we're burning VVT (Valuable Vacation Time) waiting around in the Athens airport. We're checking bags so I don't think on-the-fly standby is an option.
Do you have both flights Istanbul → Athens / Athens → Santorini in one ticket (one booking reference) or in two separate tickets?
If it is in one ticket it is Aegean's responsibility to put you on the next flight to Santorini in case you miss the one booked.
While an hour and 15 minutes is pretty tight Aegean would not allow you to book that connecting flight if they were not confident that you would make your connection. Aegean has ambassadors at arrivals who help guests get through passport control more quickly. Just carry on luggage is also a good plan to make a short connection.
Based on our experience at Athens airport we would take the risk with the short connection.
I had less than flying than that through Athens to Crete because of a delay going out of Zurich, had checked luggage, and all was fine.
I wouldn't worry but you might make sure have change of clothes in carry on in case your luggage doesn't travel as well as you.
Depends 100% on whether you have a single ticket (one ticket booked for Istanbul to Athens and all the way to Santorini; or two separate tickets - one from Istanbul to Athens, and another, separate ticket booked from Athens onward). This is critical.
Even if both flights are on a single ticket, in that case you should still have a Plan B in your back pocket (because there's a significant chance you will miss your connection). Most critically for your Plan B: when is the next flight out (on the airline you are booked with) that they could put you on if/when you miss your original flight? If that next available flight is the next day, then you get to burn one of your valuable vacation nights in Athens and try again the next day. If your airline has a flight leaving an hour later, then it'll probably be no big deal. So check their schedule to assess your risk and see how dire (or not) the consequences would be.
If you have two separate tickets, I would not risk that very short connection, unless you are willing to spend more of your VVT in Athens. In addition to time, if you're on separate tickets and you miss your onward flight, consider the cost (in money) of what you would need to spend for walk-up same-day tickets for a flight onward (because if you are on separate tickets and you miss your flight, the airline doesn't have to put you on a later flight, they can, and often will, just shrug and say "not our problem, you need to buy a new ticket" - it may also depend on what kind of ticket you bought; some tickets have some "flexibility" baked in, others are simply "use it or lose it"). It's a short flight on a popular route so it might not be a huge cost, but if it were me, with separate tickets I'd take a close look at not just their schedule, but also what it costs to buy a ticket for today or tomorrow and factor that potential extra cost into your risk evaluation.