All my orchids that are in wood baskets and have pseudobulbs get watered once a week (if weather is cool) or twice a week (if the weather is warm) in the winter. In the summer I water them every other day or at least three times a week. The media I use doesn't hold much water (lava rock, cork, tree fern fiber chunks). If your use a media that holds more water, like sphagnum, you may want to wait longer between watering. If new pseudobulbs are plump, the orchid is OK, but if the new pseudobulbs show any wrinkling, they're not getting enough water.
Another consideration is rain. If it rains often in your area during the summer, you may not want your automatic watering system to come on very often. That's assuming that you're growing outdoors.