Live ashore and cross train? Sounds like something that happens at the gym. Live aboard and cross train. Sounds like learning to do one another's jobs. When voyaging, redundancy is critical and that means we cross train to be able to replace one another.
When we sail at night, often during deliveries to and from distance double handed races, one of us is asleep below and the other on deck working the yacht. There are "below" jobs and "on deck" jobs. When the occur is not just a function of who is best at the job. It is more a function of who is available.