I remember one teacher who put me at the end of her list knowing we would talk longer. She showed me the work, but then I didn't feel rushed with other parents waiting and felt that we were able to cover everything I wanted.
On the other hand, in a more recent conference, we missed half the material because we were past the 15 min mark.
One idea is if teachers are more willing to respond to emails and phone calls, then it wouldn't all need to wait for the parent-teacher conference. Additionally, if teachers were to send a quick report every week via email, parents wouldn't need quite as much info at parent-teacher conference leaving more time for information specific to the child.
As a parent, coming with a list of questions helps you make sure you don't forget to ask what you want.