You will be informed of all cancellations or changes to your ferry schedule either by us or #operator directly.
However, in the summer months delays are normal and you may not be informed. You have a few choices when this happens.
Talk to the port police. Most ports in Greece have men and women whose job it is to keep everyone safe. They'll be more than happy to update you about the estimated time of arrival (ETA) of your ferry.
Find a local travel agency. Many ports will have a nearby travel agency. Even if you didn't buy your ticket from there, they act as informal tourist information bureau and will be glad to help you.
Last of all is the best trick. Download a ship tracker app on your phone or visit a ship tracking website. Myshiptracking.com is the site that most ticket agencies use in Greece because it gives you an updated ETA. A good app to use is Marine Traffic but this will not give an updated ETA but it will show the current location of your ship.
Please note that to use these apps or sites, you must know the name of your vessel (not just the ferry company). You'll find the name of your boat printed on your ticket or your booking confirmation (no matter where you buy your ticket from).