Once open, I think they mold pretty quickly if not refrigerated. Most of the one's I buy (Mission) come in a ziplock bag. I have noticed the toughening phenomenon to a degree but usually with the thicker brand tortillas.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250