Depends totally on where you are based and where you are commuting from.

As a VERY junior lineholder summer of 2006 I was able to hold 4 day weekend trips in PHL that were commutable on one end. Sometimes I got lucky and could swap with opentime for totally-commutable stuff.

I do know guys with 20-24 months that can get totally commutable 4 day trips...but they have a relatively good commute (into domicile fairly early and a late flight home) and work least one, if not both, weekend days.