I would opt for having someone check and add chems if it were me, and if you have someone available that can do so. They don't even have to come daily, but if they can come every other day or so, you can probably tell them pretty accurately how much bleach needs to be added. Besides, if you leave the pump on for 2-3 weeks at a time, you're going to run the risk of something plugging up the skimmer or the water level dropping so that the pump is sucking air, both of which will be deadly to your pump.