There are definite advantages to off season travel.
It's cheaper. We paid €70 for two nights in Hotel Iraklion, whereas its typical rate for our room (according to the legal notice on the door) is €120 a night.
There have been no lines.
Buses are not full.
Most businesses are open.
Locals are cheerful.
Public toilet attendants are glad you stopped by.
There is lots of soccer on T.V.
On the other hand...
Days are short.
The weather is unreliable.
Ferries run on severely reduced schedules or not at all.
Museums may have wings or floors closed for maintenance.
The highlight so far has been the ancient Minoan site of Knossos. I have been intrigued by it for years, and it did not disappoint. The public bus ride there was cheap and easy. There was no line for tickets. We were approached by only one "guide." There was only one tour group, easily dodged. The sun was out. Peacocks roamed the grounds. It was truly joyful to experience.
The Archeological Museum of Iraklion is fantastic. It presents magnificent objects in a well ordered manner. The only disappointment was that the floor housing original Minoan frescoes was closed. But we did see the figureen of the serpent priestess, the double axes, Neolithic and older goddess figures, and beautiful gold work.
Take the trip to see the Minoans. It's worth it any season.