I have a dozen or so wonderful repeat customers, that return on a regular base, to buy gifts for themselves and for their loved ones. And then I have customers that return after 4 or 5 years, saying they still use my item every single day and they think it is time for a new one, in fresh new colours.
Some of my return customers ask for extra business cards, to hand out to friends and family.
I don't give free gifts anymore (I don't think anyone ever returned to my shop because they got a free gift). And, like Sean, I noticed that none of my return customers used my coupon code (I gave that a try for a while, but stopped it too).
Me going out of my way to accomodate them with the colours and sizes they want, the quality of my products and my excellent customer service, has always been enough for them to return.