Again, the only subs that have 2 crews are the 14 Trident SSBN's.
NONE of the SSN's, the "Fast Attack" subs operate that way. They have a single crew, 100% of the time.
Deployment on a SSBN is in many ways preferred duty vs. an SSN. The entire schedule of a SSBN Trident is planned years in advance. Patrol schedules, crew changes, yard work, etc. is much easier to plan due to their schedules. At least with an SSBN you can plan about 50% of your time being in port.
SSN's on the other hand are on a much higher operating tempo due to surge deployments, special ops, etc. SSN's and their SINGLE crew are at sea far more than any other naval vessel - period.
SSN's may have an advantage in that it's possible they could make a port call during their deployment, (unlike SSBN's) but the port calls are mostly to replenish food supplies and pick-up spare parts. There are also limitations as to the ports they will visit.
SSBN Tridents will most often return to the home port they departed from - no stops in between (except load-outs, etc). Their mission is to be on patrol - undetected. They would not get involved with tossing cruise missiles as that would give their position away!
Had friend who was an NPO on an SSN. He mentioned "periscope liberty" and what sought after prize it was it was. Then he toled me what it was.. Submariners are nuts.