I had a 90g and originally bought 7 of them. I always heard they do better in odd numbers but just like everyone said they slowly diminish over time. over the course of 2 months I was left with only one in the tank. He lived for well over a year in my tank. I could just never get him out because he was too fast and didn't want to take apart all of my rock work. The only reason he died is due to a tank crash or rather temperature spike while I was out of town. Over all good fish if you want movement, very easy to care for but hard to keep in a school without most dying off due to aggression.
On a side note, mine never really schooled anyway due to the smaller size of my tank. Unless they were all scared, they would all separate and do their own thing.