Well, "entirely anecdotal" it is not! That's a very good sampling space (60-70 interviews) by, yes, a "biased researcher", one that is looking for a job which would skew the replies by the "respondents", but still excellent job, I would totally acquire your entire research report on the industry when it comes out if that was the case.

People highly criticize evergreen jobs, not without reason, but continuously doing job interviews as an evergreen job candidate is an excellent way to poke and gauge the industry, as it is of the job market, especially if it gets past the HR screening phase.