This is true. If you are not interviewing at least one a quarter (even if you’re happy at your current job) you are doing yourself a disservice. It is a skill in itself that needs to be trained and kept current. As a side effect you might get offers and jobs you didn’t even know existed.

I switched jobs twice in the last 10 years and as a result at least doublingy salary, without ever feeling the need to switch, just to keep interviewing as “seeing what’s out there”.

Also allows you to reject jobs by asking for ridiculous amounts of money, sometimes failing successfully.