Each crop is different...... I have 1 bag of first crop alfalfa that still blows up daily.  Corn silage is normally a touchy crop here.... I tend to watch those bags daily.  I have had them look smooth like a hotdog before.... and vented them a bit more each day as it concerned me.  

I've never had one blow, but some sure have scared me that they would.  

As was advised.... an X cut will do the trick....