I think one of the issues with plastic bags is that if there is any moisture, the moisture does not escape and mold can grow. I think that is way it is suggested to not store fabric or quilts in plastic bags but rather in something that will allow some airflow like a pillow case. I live up north so moisture is not a problem in winter...have to run a humidifier so my nose doesn't dry out. but I don't store any fabric in the basement as that does get damp in the summer.