As far as I can tell, the "reset" is individual and 18 hours after the last one was gathered. I wait at least 18 hours after my last map gather, so I wouldn't know if it's really sooner than that. I use Botanist at Lv50 nodes, and it seems random whether a map appears in the node gather list, and random which map type appears. Early on it appeared after the first few tries but lately it can take many attempts and 5-10 minutes before I see one. If the "wrong" type of map appears, I don't gather it, and another map appears after several more attempts.