Had that issue ourselves.
We clean a premises on a Tuesday and Thursday evening, they complained about cobwebs, ( which spiders produce in hours).
I had to explain that at night, by the light of their new 'Energy Saving Bulbs'
it's not as easy to see cobwebs as during the day with lovely sunshine streaming through the offices.
They also mentioned some dust, so I had to explain that when the girls leave at 9 on a Thursday, the office is then NOT cleaned on Friday, Saturday, Sunday, Monday or the daytime on Tuesday, effectively 5/7ths of a week.
Sometimes you do need to explain the bleeding obvious !
Les
Oh, and one 'ex' client wanted to know how long the girls spent cleaning a door handle in his Food Factory Unit as it was getting dusty... I told him about 10 seconds and then worked out how many seconds in a week it wasn't cleaned between visits and told him next time I saw him.
Unfotunately he never could seem to pay our invoices on time....probably couldn't see them for the dust
so we left !