My brakes on my 1996 jeep cherokee started dragging yesterday?

they started dragging all of a sudden just enough to be able to hear them dragging and smell them burning both front brakes are doing this not just one any ides to what might be causeing this if i take the calibers off and compress them with a C clamp and put them back on they will dont drig for about 15 or so hours them they go back to dragging plz help i was told that my rubber brake lines are bad and to repleace them the brake fuild in the resavoir is very dirty