IMO, the most revealing moments in the FBI interviews were those instances when Keyes was describing various killings. JMO, it's not "restlessness" that overcame him in those moments, it's agitation, desire and possessiveness. He could re-live each murder every day if he so chose - and I believe he did - but he did not want to share the intimate details with anyone else. Not ever. Those couple of times when he had to describe a killing, per his strategic choices around bargaining for the death penalty, it was really difficult for him to narrate the event while at the same time keeping the experience completely his own private property. He had to work hard to conceal his arousal, which was still immense all those months later.
Maybe he would have revisited victims, but I don't think he needed to. I think he had all he needed in the scenes he could replay at will. I think he replayed a couple of them right there in front of the agents. Chilling.