I also red once on an spanish defence magazine that the other "problem" with the nuclear powered carriers is the escort.
While the engine endurance is "unlimited", the carrier needs to be resuplied with food and water. And the escorts need also fuel.
And there's other thing about non-superfast nuclear carriers: some escorts could not follow it so, where's the need of developing a faster carrier? That only will be a waste of time and money (and probably reactor safety) for having a 40knot carrier wich could never use that speed.
That magazine also compared the time spent on deploying nuclear and non nuclear carrier groups from its bases... and the difference was very few...