So what happened to make island-hopping so difficult? Isn't this what going to Greece was all about? A couple things happened. First of all a couple major ferry companies bought out everyone else and with their new beautiful boats did not want to waste them on un-lucrative routes. Then as older boats began to retire the ferry companies did not have the money to replace them with new ones, so there were fewer boats. The ferry companies are also very protective about their markets and fight to keep other companies out of their islands. So you can stand on a mounttop in Sifnos and practically see the white houses in Paros, but to get there you have to go back to Pireaus or in the summer wait for a boat that comes a couple times a week. In the summer there are routes that make it a little easier, because there are more people traveling. But if for example the boat that does a route than connects a couple islands is losing money the ferry companies won't ride it out. The boat is broken. Engine problems. Whatever.
So you can still island hop. If you want to just take your chances and get on a boat to one of the popular Cyclades islands there is a good chance you will be able to make connections to two or three others on your list, though sometimes ferry connections have a strange way of being wrong for you. For example you want to go from Kea to Sifnos so you have to connect in Kythnos, only the boat from Kythnos to Sifnos leaves twenty minutes before the boat from Kea to Kythnos arrives. Sometimes it seems like someone with a real sense of the absurd made up the ferry schedules, like there are 3 boats leaving from Pireaus for one island at the same time and no more that day. Or there are only three boats a week from your island to Santorini and one of them is on Monday and two are on Tuesday and today is Wednesday and you just arrived. Someone shouls make a book of ferry connection stories.
Anyway you can avoid problems by either choosing an island program with the islands that are on the top of your list by working with a travel agency in Athens. Actually you won't be avoiding the problems, you just won't be aware of them because they will be dealing with them. So for example you wanted 4 days on Mykonos, 3 days on Paros and 5 on Santorini, but instead you got 5 days on Mykonos and 4 days on Santorini. That's because your plan had to fit the ferry schedules. Try www.greecetravel.com/create-an-itinerary
Anyway island-hopping is over-rated. If you have a week to ten days on the islands pick two islands and make the most of them. One problem with seeing lots of islands is that once you get comfortable and have made some friends it is time to move on. If I can spend three months on Sifnos or Kea you can certainly spend a week or more in Mykonos or Santorini. You won't run out of things to do. In fact you may decide to come back next year too.