I think it's very important to make the goal reasonable for all participants.
BUT-as Autumn noted, the participants have to be reasonably motivated to actually do the "training" required for the trip.
My 17 year old sister is signed up to do a week long trek through Denali State Park (Park where Mt. McKinley is located). There is 4 months of classwork and training to do before the hike.
Each student is expected to do this classwork and training on their own before the hike. The coordinators of the hike make the information available to the student, but they can't enforce the learning.
SO-if the student shows up unprepared, where's the breakdown?
In our relationships, if we have allowed significant time, found the resources to read, study and meet other poly-people, followed agreed upon "temporary boundaries, etc.....
at what point is the "slower person" held accountable for not choosing to make use of these things in order to work on their own insecurities, communication failures etc.... ?
"Love As Thou Wilt"