LOLI contacted Scuba Club in Cozumel, but they do not allow multiple night dives because "the shop closes at 6PM." @Doc Harry
Just pull as many tanks as you need for night shore diving before 6 pm. Put the tanks in your locker if you wanna get paranoid. Dive all night long if you want. I've done multiple night dives at Scuba Club over the past 20 years. I like to go out right at dark, and then jump back in for another night dive at around 10 pm. In April we had a group and pulled 10 tanks before 6 pm.