Authentic assessments give students the opportunity to connect the content in any unit to real-life activities. 

If you are concerned about time (and who isn't these days?), introduce the assessment at the BEGINNING of the unit. Students can be processing it and planning as they work their way throught the unit. This will cut down on the time needed at the end of the unit.

Don't shortchange your students by eliminating the Authentic assessments!  This is a vital part of the Rigor and Relevance framework.