Book Greek Ferries ahead of time?

Travel Info
I will be travelling to Greece From mid JULY to MID august
I will be visiting Athens, Paros, Mykonos, Santorini, and milos. Do I have to book the ferries ahead of time or shalll I wait until I get there?
thanks

Travel Tips

If you are planning to bring a car with you definetelly book them. (by the way you might be late already)

If you plan to take High speed boats book a couple of days ahead.

If you don't have a car and you are not on a tight schedule don't book them. You have chosen very popular destinations and there are always ferries there. At worst you will have to wait for the next one.

Mind you, ferry companies give (some times substansial) discounts if you book ahaid of time. Check it out.

Others
It's really up to u ! All of the islands u mentioned are really popular so there are many trips per day!!! Also there are 2 types of ferries the fast ones and the normal. To get the idea with the normal (which is much cheaper) to go to Mykonos is about 5.30->6 hours with the fast is 3!!!! I'd think u better booked definitely if u have a car or u want a fast ferry and to be sure u'll find a ticket the date/time that's convenient to u.
Here some sites:
http://www.hellenicseaways.gr/
http://www.bluestarferries.gr/
http://www.milostravel.gr/

A! Since u 'll go to milos DEFINITELY make the tour of the island by boat!!!!
Go with the flow . . .
do it as the Greeks do . . .
tickets you ll find
the only risk is they might be a bit more expensive . . .

just get there first!
If you ll have a problem getting to an island the most possible is that you ll still have the same problem with tickets or not. . .
I don't know if I'd recommend doing that. Greeks go on strike alot. I'd probably wait til I got to Athens and buy them a few days in advance, at most. Also, by waiting, you can spend more time on the islands you like and less on the ones that may bore you.
Its better, if you know the exact days of your travel to book/ buy them ahead of time, just in case everything would be sold out, last moment!
In case you are interested, send me an email and i will direct you to a travel agent I trust!