The 72 hour border visit maximum has been around for decades, long before the border zone was extended to Empalme and including Rocky Point. It is still in effect even if rarely enforced, but can have severe consequences especially for full time residents who unknowingly violate it year round. I have seen it enforced only when the authorities had it it in for gringos who have been a thorn in their side. I wouldn't be expounding on it myself.