1.5 days in Athen - Should we add a night?

Hoping for some advice. We have never been to Athens. We are on the Vista in October and will have an overnight in port. We are thinking to hit the main sights on the first day (Monday), and then the second day to take a tour that will pick us up from the port and do a tour of the coast and then take us to the airport for our 4:40 flight to London. Is this enough time in Athens? Or, should we add a night in a hotel on the Tuesday, and fly out on Wednesday instead?

Thoughts? Worth it, or not worth it at the end of a port intensive 10 day??

We are flying on to London for a couple of nights with family before flying back to Edmonton. Thanks!

"Worth it" is a personal judgment call only you can make.

That being said, I would take the extra day. I have yet, after decades of traveling, both on cruise ships and land tours, to tire of spending time in special places like Athens.

You don't mention what your "must see" sights are in Athens, but keep in mind that certain sites open later on Mondays (including the Acropolis and the National Archaeological Museum) and others are closed on Mondays altogether (e.g., the Acropolis Museum).

If it were me, I'd plan to stay the extra day.