So here is my take on it and I've fed pond electronically for a lot of years.
You need the feed going in in the eve not the morning to encourage the ducks to arrive as its going dark and not have all the vermin eating your barley.
The reason you set it to go off a good half hour before dusk, is so the birds arrive before dark, so you can see to shoot them.
If the feeder is set off by the light going, it will frighten away any ducks already there! and they will come back in the dark-Ive had first hand experience of this.
Then we come to the distance thing, some of my ponds are 30 miles away, Im not going to visit everyday either! but you have to visit once a week at least, for even a 45gallon drum feeder of barley wont last much more than that [if you have any ducks]so when you top it up you change the time again, 30 seconds of your time! simple.