Another important misconception about Prefer Off weekends, it does NOT (as another poster stated) try to give you as many weekends as possible. The language in PBS is a misnomer i.e. “Prefer Off weekends minimum 4” means that PBS will attempt to give you 4 weekends off and 4 weekends only.

I prefer using Prefer off Saturday and Prefer off Sunday, and even then I only use it for my default bid.