Whether the length of a thesis is a mark of quality is a subject that is treated differently in different fields and universities. While it is universally accepted, in some fields e.g., the arts and ecology, that a well-researched PhD thesis ought to achieve some number of words, some fielded e.g., mathematics and physics, may not place a lot of emphasis on the length of PhD theses. What is your opinion of this subject, and what is the practice in your field/ institution.