See #49.
Okay, there's not really a blanket answer to that question. As much as I like to make fun of the boomer guys, they had a strategic mission that had entirely different demands from SSNs. Having to get a boat turned over to another crew and back to sea in a month was no picnic.
SSNs have a more tactical mission, so we went where operational requirements dictated. They're not "out all the time". Brief, frequent underways between deployments just makes it seem that way. My personal best is 284 days in a 12-month period, but most of the time it wasn't quite so much.