We offer a 30 day guarantee on all work.(after 30 days, another spray is another charge unless you are a full program customer). I tell the customer this up front. If you haven't wasted some weeds in 30 days, you didn't do the job right the first time. Setting expectations from the beginning is the key. I at least try to talk them in to the Spring and Fall pre/post and most will do this when I explain the benefits. Besides, these are the most profitable apps we apply so how can we turn them away...as long as like I said before, it is scheduled at our convenience. Also, like Riggle said, it offers future opportunity to upsell.