We cut out the pest control, because I'm a mostly-organic gardener and I didn't want the chemicals around. Of course, it was like an open invitation to ants. And while they enjoy the cat food (once we went out for the day and had fed the cats before we left, and one of them threw up, and by the time we came home, a mile-long line of ants had made their way into our house and were bringing delicious vomit back with them), they come in everywhere.
This year, it was the bathroom. WTF, there's no food in the bathroom!
I finally gave in and bought some perimeter spray at the hardware store. It works well enough and is a lot cheaper than hiring someone. It needs to be renewed more frequently than the professional stuff. Diotamceous Earth was my first shot, but it didn't work.
I also take a walk around the outside of my house every week and look for ants that are getting into the siding, so I can spot treat.