I've just completed 3 weeks away from the good lady for leadership and, to be honest, it was hell. I didn't like being apart from her and it was the same the other way. However, daily email contact was a big help and kept me away from drinking and any temptations that drink might bring.
As iterated, it does depend on the individual.
Navy has changed a lot, HMS Royal Arthur Corsham cost most of us a small fortune to complete the leadership course, and it was 6 weeks long not three. I always reckonned that there should have been a special entertainment and socialising payment while on course