I would always ask for updated LOR's, even if the information is pretty much the same. Part of it is being collegial and maintaining your network with your references... that you weren't using them just for getting a letter.
However, I would talk to your premed advisor (like me) to see if there should be a particular focus that the recommenders could address. Sometimes, those faculty or general references are generally positive but do not address the characteristics of being a doctor that the admissions committee is looking for. That way, when you do ask your references for updated letters, you should be sure that they specifically address those qualities that make you a good health professional.