I guess you northern guys don't have bed issues with spurge, chamberbitter, purslane, and sedges.
you can rape a bed down to the soil, apply 4 inches of mulch and within a week have seed pop up from chamberbitter, spurge and sedge. It must be my hot temps, but come on lets be real. Sometimes tilling isn't a reality in densly planted beds even with line trimmer cultivator's and the mantis.
As far as the customer, yes go back and reapply some gly and kill the weeds before they reseed. As I said above, if you don't get some of these weeds before they seed drop, then the irrigated beds will only reoccur and cost you more trips. Geotextiles is good for a while until seeds grow on top of the mulch layers. I guess I don't understand the comment of paper!!!! You mean applying newspaper as a base layer to keep out weeds?? HMMM! Never did this other than to provide a moisture barrier for my garden and to solarize a pathway. Other than that, the paper will break down and serve no purpose.