The meshtastic team seems to generally agree that if your channel utilization is over 50%, you should be dialing up to a faster preset. So I probably wouldn't do anything more than say 25%.
I think some other fair restrictions would be that you absolutely must be directly connected to it with at least zero hops. You cannot go through another mesh point to get to the node.
That would need you to physically drive to within probably about a mile of the node itself, which is still better than climbing the 200-foot tower, as you mentioned, but would keep the local mesh from just dropping out of the air while updates were occurring.