philosopause

Etymology
from

Noun

 * 1) The informally observed tendency of mature or elderly scientists, who apparently have outlived their most productive years of research and similar practical work, to discontinue or decrease their participation in such activity, in favour of pursuing, and often publishing, philosophical theories or speculations. Commonly the implication is that such works are beyond the authors' recognised field of competence, and, as a result, typically of disappointing value or standard.