each search is done on the same timer, so the fewer searches done, the more frequently you attempt the same link. Tailor that to whatever you're attempting to work on. Higher paying surveys are being put on PC at a 1s refresh by most, and targeted directly without any other searches, so searching once every 10 seconds isn't likely to catch you anything. With 5 or fewer searches going, you're effectively doubling or tripling your likelihood of catching something.
There is a search function built into PC, and some ways to manipulate it, all of which is covered in the documentation