I dunno,
I expect they will come cleaner with periodic cleans. It depends what the customer wants, expects and what you think is right. You are using facelift can you angle the brush down for the cxap on the sills, next time before you do the glass. Mind you if you have detailed them with a cloth you wont need to do that next time.
Dont get to paranoid over the results or they will have you jumping thro hoops. Its a balance.