I dont think it will take 72 hours to get back to 30day luck. More like 1week.
72h was about our weekly luck to recover.
Unless my calculations are a bit off, I thought that with neutral luck, we should expect ~7 blocks daily - the CDF hits 50% at 3 and a bit hours IIRC.
You are right. I was sleepy and calculated the time with the current network speed, while it should be at the time of the difficulty change, so 20PH instead of 27PH and it's ~5.6 rounds per day or ~4h 20min per round with our current pool speed.