Here’s an example of why it makes sense to use smaller coupon sites and skip Groupon if you are looking for a lasting customer.

Lisa Gurvich, owner of Lasoderm, a laser hair removal practice in South Miami, has done deals with two sites and found the smaller one to be more effective at landing long-term customers.

MyCotorra.com, a small site based near Miami approached Ms. Gurvich for her first deal. Together, they devised the offer: $89 for six sessions of laser hair removal. Ms. Gurvich asked to limit the deal to specific body parts and to one deal per person. More than 100 people purchased the coupon. Ms. Gurvich offered another discount for a future treatment, which about 40% bought, she says.

Ms. Gurvich then did a broader offering with Couptessa.com, a much larger site with nearly 100,000 subscribers in South Florida. It delivered a crowd of what she called coupon addicts—customers who bought several deals from a variety of sites and would bounce from one practice to the next. Couptessa says that half of its affluent subscriber base has become long-term customers for many of its clients.

Ms. Gurvich has since signed an exclusivity agreement with MyCotorra.com. “The tiny site has worked wonders for me,” she said.

The sustainability of the coupon-site business model depends on the extent to which both sides benefit, says Jimmy Hendricks, co-founder of Deal Current, a technology company that provides daily deal software to publishers. Generating repeat traffic is among the biggest problems for daily deal sites, say small business owners, many of which only make money when customers return to pay full price.

After a couple of deals, children’s clothes-swapping site ThredUp decided to open some of its offers only to new customers. To redeem the deals, buyers had to enter an email address and voucher code on ThredUp’s website. That allowed the company to go back to those customers.

“We’re able to re-engage them at any point,” says Karen Fein, marketing director.