I was looking through the forum for last year. It appears that some received their tentative offers as early as mid Feb (2/16), spanning to as late as March. I would say if it is getting to the last week of February and you haven't heard anything then you should be able to call. They said that Carter Kimsey was nice and responsive, until things became very busy. Also, formal rejection offers were even more delayed.
The anticipation is making me nervous. Fingers crossed and good luck.