We have 18 nights in Spetember (yippee!), the first and last need to be spent in Kos. We'd like to revisit Patmos and I am finally going to return to Leros (hey, it's only been 17 years!) - we're also considering Arkoi. I've read Mitnic's page and Arkoi is definately edging it's way on to the itinerary - but how many days would do it justice? I'm guessing 4-5 to soak in the atmosphere, do a few walks and generally chill. Any advice?