Nope, rarely happens.
The odd time I may get a text back from a customer who I let knew I was coming (for the gate to be unlocked) and they may say their on holiday and if I can skip the clean.  Yet this happens rarely and isn't a problem.   If it's an eight weekly customer, he/she will just get rebooked for 4wks time rather than another 8.  Its not a big deal really.