My gf pays me to do them every 4 weeks inside and out - she then puts the costs down for her own expenses as working from home..LOL
you should be a labour polititian

do mine every fortnight whether they need it or not
cant see the point of having a sign on my wall and a signwritten van outside saying i do window cleaning and then leaving my windows to get dirty.. picked quite a few jobs up as people walk past whe im cleaning them