yeah, work the other way... when does the pot need watering? that's your trigger, not a pre-ordained schedule of your choosing.
as far as duration, that too depends on flow. if soilles, observe and time it / adjust until you get ~10% runoff from slowest pot. that's your duration as long as you irrigate at a similar dryback. Can always err a bit longer, if not present to supervise. Simply watch it and be consistent about when you re-irrigate -- same loss of weight from pot = same volume of water needed.
in some situations you can predict amount of time between irrigations. You can even get familiar with how it ramps up as far as plant size relative to pot size and how you pot up, etc. I generally know when i have to irrigate, but as the plant is growing and increasing pot sizes, it's not a consistent amount of time until a week or 2 into flower for me, YMMV.
Strongly suggest supervising any irrigation system and only relying on it unsupervised as necessary... not for a trip to the post office. It may run smooth for a long time, but the moment it fails it's a fucking catastrophe if you are not there, lol. Shit gets clogged, some equipment fails... it is inevitable and you don't want gallons of runoff water on your floor.
I once walked away from a rez refill and started doing odd tasks in the tent... dumped about 50 gallons where rez was located, lol. I now stand there the entire time while it refills, because i'm absent minded AF.