Specifying a recommended time between washes is non-sense. If the mirror looks foggy or unclean - wash it . Refractor users would not let their lenses get into the state reflector mirror owners tend to let their mirrors get into. Why ?
Better still let your mirror become a cess pit - take astrophotos then post a picture of your mirror so people may marvel at how good your pictures were with a dirty mirror
http://www.iceinspace.com.au/forum/a...e.php?a=145670