Barry SchwartzGoogle's @searchliaison says don't delete old content if it is helpful content - Google doesn't dislike old content he added https://www.seroundtable.com/google-dont-delete-older-helpful-content-35846.html
SEO grandpa (Michael Baggelin)@rustybrick @searchliaison well , I would say that search and research has different purpose. Old content is both useful and helpful content. #helpfulcontent #research #search #usefulcontent