My grass is broken up into 4 zones. Sometimes I wonder why I couldn't be on a single zone, but that was the way they set it up when the house was built. Half the grass does tend to get more sun, so that may be a reason to run the sprinklers a bit longer.
I don't really worry about changing the grass type twice a year, as that's not a huge deal. However upping the watering frequency and duration for a short period when I overseed has always been a bit of a pain, it is always a balancing act between keeping the seeds and grand damp, and overwattering and washing the seeds off.
I wonder if there could be a setting for when you put down new seeds, that would last for two weeks, and then start lowering the frequency as the seeds begin to take.