As a vacation diver, I don't usually have the luxury of repeating a site many times. There are a lot of sites I can think of that wouldn't bore me if I dived them twice a day for a month. When I lived in Singapore I used to make frequent weekend trips to Phuket, so I have at least a dozen dives at each of Shark Point, Ko Doc Mai, Anemone Reef, Racha Yai, and Racha Noi--the spots the day boats go to, for the most part (along with King Cruiser, I guess). I have maybe ten dives at The Elbow in Belize. Places like Sipadan and Layang-layang lent themselves to repeating a site--they're small atolls, so if you were there for a week (no longer possible at Sipadan) you might hit one site at least once a day. I did the "house reef" each day, and we hit the same spots with the skiff each day too. We had good hammerhead action at one site at Layang-layang so we kept going back, twice a day for a few days. We would have done more but it was deep. Simiarly, Manuelita Outside at Cocos was the go-to site when I was there--that's where we were seeing the most hammerheads. I probably have the most dives on the beaten-up reef in front of the Harbour Village Beach Club in Bonaire. It's not much of a site, but it's too convenient to pass up when I'm staying there--just wade in.
There is value to repeating a site, especially to a macro photographer. You will know where to look for the octopus, the yellow-headed jawfish incubating eggs, or the juvenile angel that seems willing to pose for you, so you can keep going back until you get the shot that you want.