Scheduling is handled by the distaff members (legal wife and common-law wife, A and A2, whatever...). We've found that works better and avoids any feelings of 'being rejected' or 'favored'. (The two are sisterly in their relations; they don't always get along, but they always manage to work things out.) The family joke is that harem slaves are expensive and hard to find...
We sleep separately; I'm a very restless sleeper and they find it hard to get any rest if I'm sleeping with them. 'Relations' are generally one-on-one, with exceptions for special occasions (such as birthdays).