I'm ambivalent about this kind of advice. On the surface it seems right, and I've never been more comfortable in interviews than when I was thinking "I don't need this job", at the same time interviews are incredibly stressful time wasters. For a lot of people, interviewing is one of the most stressful situations they are going to be in, barring life or death situations.
Just the thought of 18 to 30 interviews a year makes me anxious and I don't even need to interview now.
I'm not a young person anymore, and interviewing more is not going to help me either. It's like pulling my teeth: not something I want to practice.