I'm trying to get a grasp on distances here before I book a hotel.. (I'm leaning towards Aris Caves in Oia). How long does it take to travel between Oia and Fira? Is the best means to do this via bus? And at what time in the evening do the buses stop running? Thank you!
By bus it takes about 30 minutes at most. The bus schedule changes with the demand, running later during the summer months. The last time I was there was in May-June of 2007. The last bus from Fira back to Oia left at 9:30pm. In July and August there will be buses back until sometime around midnight. After that you'd have to take a taxi. The road is treacherous at night if you're thinking of a rental car, especially if you've been partying.
Here is a link to the island bus schedules.
I walked between Fira and Oia in two hours. It was beautiful along the Caldera and I got to Oia in time for the Sunset (and the applause of everyone awaiting the event). I wouldnt' suggest walking at night it is quite dark between. I took a taxi back to Kamari where I stayed at the Larvis Hotel. Quite a bargin for Santornini with a location near the black sand beach. The only problem is that Kamari is even farther from Fira. You will have a wonderful trip.
One question to sneak in here... is there a place to go to check on taxi prices from Point A to B on Santorini?
Jeff, is the walk from Fira to Oia a fairly easy two hour walk?
No. Taxi fares vary from 25 euro down to about 5 euro depending on how far you need to go.
Additional info on walk along the Caldera between towns:
I was traveling with a group of eight including two 60 year old people in reasonable shape. Nobody had a problem. There was no steep uphill really just slight upgrade in elevation in the middle. The pathway takes you on the inside of the caldera by some beautiful hillside homes, tiny chapels and look by your feet to find wild herbs growing everywhere.