Ok, so I've done some science to figure this out.
There is a process to how nodes respawn. After two hours of testing, I believe I've determined how it works, and what you can do to maximize your rare item gathering.
Here are some things I've learned:
- Nodes respawn at three minute intervals. I tested Moga Woods, Deserted Island, and Sandy Plains, and all three of them have three minutes as the respawn time. I expect the rest of the zones to be the same.
- Fixed nodes are outside of this timer. They spawn when you enter the quest, and don't disappear until you've gathered their maximum limit. And they don't respawn, so that makes them one-shot deals. Nodes in Hidden areas are fixed nodes.
- To the best extent that I've been able to test, nodes do not respawn unless you're in the area. Your presence is what causes nodes to (re)spawn. You're not there, nodes don't spawn. The timer pauses. If you had twenty seconds remaining of your three minutes, it will take twenty seconds once you re-enter the area for the nodes to re-spawn.
- From what I can tell, each area and node type picks a random amount of time (within those three minutes) you first have to be in the area before the node will spawn for the first time. It could be zero seconds (in which case, the node will spawn as soon as you enter the zone), or it could be right at the three minute mark. Two different node types can pick the same time.
- The node will respawn once it hits the designated point in time, regardless of if you've harvested it or not. The node will despawn at that point to make room for a fresh node.
- Every node has several locations at which it can spawn. Location has no bearing on what you harvest from it. Only the node type alters that.
To maximize your chances of getting rare items like Carpenterbugs, here's what you want to look for:
- An area that has as many non-fixed gathering nodes as possible. For Butterflies, you're in for a hard slog, as no area seems to have more than a single node that will respawn. In those cases, you want to choose the area that has the best chance of giving you that item.
- The Gathering or Felyne Gatherer skill. Most nodes have a variable number of times you can gather from them. And the Gather skills will ensure you get as many items as possible.
- Depending on the number of nodes you'll be gathering from, you may want the Speed Gatherer skill. If it takes you longer than three minutes to gather every node in the area, this skill is needed.
- Whim and Felyne Woodsman (or extra Mining Picks/Butterfly Nets/Fishing Harpoons) to ensure you get as many items as possible without breaking your gathering items. Nothing like whacking a mining node and have your last Pickaxe break on you.
- Mostly, patience. If you've gathered every node in the area, and nothing has respawn yet, be prepared to wait. They won't respawn without you, so you have to stick around. Kick Back, Dance, Prance, whatever. Stay in the area, and remember that the node doesn't respawn in the same place everytime. Keeping an eye on where it was before doesn't guarantee that's where it'll respawn. Look around the area.
- As far as I can tell, every non-fixed node will respawn. If it's been three minutes, it's back, somewhere in the area.