I have five lawn zones which this season I split into 4 schedules. I use flex monthly BTW. Last year I ran these all in one schedule, but when I did that, the frequency of when the schedule ran was dictated by the zone with the most sun exposure, of which it has a lot. This meant the shady zones were watered more frequently, albeit for shorter periods of time. I was also fighting mushrooms a lot.
This year I decided to try splitting them up except for two zones with similar sun exposure. This allows the controller to run each zone as frequently as needed for, I assume, the “correct” amount of time.
I run all of these schedules to “end by” 7AM and have had no incidents that I’m aware of where “stacking” (which does happen) has created any run problems.