Most impressive regular season run at the top since...?

Being #1 obviously puts a target on your back, and this UK team has withstood the pressure unlike many in recent seasons.  This week, UK will remain #1 for the 7th consecutive AP poll.

Over the last few years, a number of teams have put together equal or better streaks:
2005-06 Duke = preseason #1, plus 10 additional weeks
2007-08 UNC = preseason #1, plus 10 additional weeks
2008-09 UNC = preseason #1, plus 7 additional weeks
2009-10 KU = preseason #1, plus 8 additional weeks
2010-11 Duke = preseason #1, plus 9 additional weeks

The obvious caveat here: all of the above streaks began at the season's outset, when it's arguably easier to retain the #1 ranking against an often-shoddy non-conference schedule.  Sure you might be tested in an early-season tournament or in-state rivalry game, but you won't be challenged as consistently as you are during the conference schedule.

Therefore, I think you have to go back to 2004-05 to find a run at the top more striking than this Kentucky team.  That year's Illinois team stayed at #1 for a remarkable 15 weeks through the heart of the season, before going on to lose in the national title game.