How long should a successful rebuild take?

2005-2006 Saints took one year.
The 2005 season was the biggest outlier in NFL history! Move the team headquarters out of state, play every home game NOT in the home stadium, every player dealing w/family/home uncertainty, a fan base that was still shell shocked by Katrina & a coach that knew the handwriting was on the wall!
In 2006 w had an awesome draft, a new coach & the best free agent signing in history of the game! The dome opener against ATL was a cherry on the top! After that season it took a couple more years to consistently get it going.