Your right about the the mugs and calendars. Not a bad idea. I still think it is about 12 times, and that is according to some of the great guru of the past. That is all on things. Print, classifieds, and other media. People do not have a large span for ads, that is way you need about 12 or even more. Look at Radio and TV ads, You see the same ones every day again and again.
Just 3 might work on occasion but that does not mean 12 is not best. You have test and test and test and see what works for you. I have had display ads work great for free stuff. But paying is something else. The display ads for free work in day one. But that shows nothing. Even a newspaper editorial by me worked the first day with the phone off the hook. That was again FREE. Did not have anything to follow through at that time. Kept the names and numbers thought. That was for bars. Bars are always looking to make more money. Some don't make much at all.