if the leaves are coming down THAT hard in one area where we think the lawn will be covered right after we leave or if the wind is blowing THAT hard, we often move to a different area to work that day or perform a different service. we usually do 2 huge leaf cleanups at each property in the Fall after mowing has slowed. the results are obvious when we leave even if leaves are still falling.
sounds like your customer is a PITA. i would either reconsider the conditions in which you do leaf cleanups or find customers that don't question your integrity...