Yup that's why I use them...just to stretch it out longer. Mine are pigs. Even the stuff that falls to the ground they will eventually get to but it keeps them busy longer and in the winter, when you use hay for internal heating, it's nice to see them munch on those hay bags for several hours vs. 30 minutes.
QtrBel, it's been a while since I've looked into them but here's one website that sells them. I'm sure there's others. They're even in TX. Not sure where. They're not cheap but it sure sounds like a neat idea. When I was using round bales, I had to really ration their time out in the field with that round bale or they would burn through it in less than a week. With 4-5 hours access a day, I could make them last a couple of weeks. I never did the net thing due to their price tag. I've always wondered about making my own though. :)
Here's the link Texas Haynets - Texas Hay Nets - Home