If you are looking for the very, least expensive time to take an expedition cruise, then consider sailing between the end of August and before Christmas, but not over Christmas or Thanksgiving.
* Most families have children that are back to school
* Folks begin saving vacation time
* Everyone's saving money for the holiday season.
Considering all of these factors, expect adventure cruise prices that are better than 2-for-1 with reduced rates for 3rd and 4th passengers.