Self Drip Irrigation System

I would like to make a couple self drip irrigation systems using 1 gallon jugs, I've been reading about them but nobody really says when you need to re fill them, the location i'm going to be putting them is a good distance from my house so im just trying to be efficient and make as little trips as possible, what would you guys say a good rule of thumb is for refilling them? my plants are about three weeks old also

Bunch of variables there: how fast the drip, how big are the plants being watered... My experience was w/a 5g bucket and two small holes (1/16") drilled in the side at the bottom. It would take almost a day for the water to drip out.