You can visit most of the art in one day, although two days is better. On top of the museums the House Art Project and Naoshima Bath are worth a visit, not mentioning all of the outdoors art around the museums.

However, one common misconception is that the Benesse Hotels are the only hotels on the island. They're not. There are also a few more places to stay in the villages, as well as the campground near the Benesse House where you can sleep in Mongol yurts.

Also, it's a big mistake to go to Naoshima and not to its neighbor Teshima which houses less art for sure, but which is in my eyes more interesting (but that's personal).

Finally, I need to mention that the Setouchi Triennale 2013 will take place next year (in March-April, August and October) and will involve most of the islands in the area. It's an event that must not be missed for art lovers.