Since the comet is sending a mineral packet every 5 days, I'll gradually see an increase in transiting material, but I should recieve a new packet every five days like clockwork, even at the extreme end of the orbit.
Thats a good idea to send it to the moon.
Actually, when the comet is travelling away you will receive a packet every slightly-more-than-5-days, as the distance the packet needs to travel will be a little longer every time.
Then, on the return trip, the packets will arrive every slightly-less-than-5-days. Luckily the comets travel a LOT less than 1000km/s, so this is probably negligible.
That does raise an interesting suggestion, though. I can't find comet speeds listed anywhere. Is there some way to see how fast they're going? If not, could that be displayed on their body info? It would make it easier to judge how long a comet is going to be in-system.