Please don't take my comments the wrong way, but do you not close the deal when you visit to do the estimate?
At the point when I provide pricing to my potential customers I discuss dates, costs etc.
"I can start on Monday the ??th, is that date convenient to you?"
"Is there any reason why we can't book a date now?"
"When would you like me to start?"
"I've got 2 more quotes to do today, can we fix a date now, or are you happy to wait should I win these other quotations?"
"I've got a space in my diary for next week after a plumber let me down, if it's okay to book you for that week, I'll include the materials for free?"
etc, etc...
Not teaching anyone to suck eggs, but close the customer there and then and you'll sleep a lot more comfortable.