ya know this is a GREAT Question.....
When I started in a NEW area. I passed out flyers when I had nothing to do.
got some calls from them, really didn't keep stats on it. But a lady called me several years after I did this. and she said she had one of my flyers. and when I got there, I be Dammed, she DID !!!!
she had to of had this flyer for 2 years at least, this really BLEW my mind.
Also: From time to time we pass them out in areas where we need to build up more customers.
best of luck to you