@Jessica Bradford good question and honestly one I don't see come up enough — most people fixate on whether they *can* reach that distance and never measure what happens to latency once they do.
Short answer from what I've seen: at the far end of the envelope the dominant factor isn't propagation delay (radio waves at 40km adds maybe 130µs, which is basically nothing), it's the link layer behavior — retransmissions, connection interval, and how aggressively the radio is backing off when RSSI gets marginal. So "variable depending on link conditions" is the most accurate framing. On a clean link with good LOS you can stay in the low-to-mid hundreds of milliseconds range, but if you're at 40-45km with any interference or antenna geometry issues the stack will start retrying and that's where you can see it stretch into the seconds in worst case.
The connection interval parameter is worth pulling up if you haven't already. At those distances you're probably better served with a slightly longer interval to reduce the frequency of failed attempts rather than hammering the link trying to hit a tight timing window. What's your current packet size and connection interval set to? That'll change the picture a lot.
