Standard words...

So, I've decided that one of the things that upsets me most in academia is when scholars decide to change the meaning of words.  For example, James Webster, in an otherwise very interesting article on how to look at the periodization of music, particularly in the Eighteenth century, questions the characteristics of a century.  Now, to me (and I would guess most readers) the word "century" means a period of one hundred years, from the Latin centuria meaning, to divide into 100.  That Webster feels he can redefine a century irks me.  Webster writes: "... a century can be construed as having either begun or ended before or after the centenary, and also as having been shorter or longer than one hundred years."  (Webster, James.  "The Eighteenth Century as a Music-Historical Period?"  Eighteenth-Century Music.  1:1, 47-60.)    The first part of this statement is fine.  In no way does a 100-year period have to begin and end with years ending in 00.  However, to say that it can be longer or shorter than 100 years???  Can't we leave definitions of words that have been in the English language for 500 years alone?  We do have other words used to describe periods of history...  era, period, epoch, age...  why mess with the length of a century?   I can even get behind the descriptions of a long-Eighteenth century, or a long-Nineteenth century - there is a qualifier there that helps the reader to understand.  But, if we are trying to make our academic work relevant for the non-initiated reader, can't we let standards of measure be that... a standard?