Resort spas count on supplementing their overnight business with day guests. However, they may be suffering from "too much of a good thing." Industry studies indicate that some resorts have become so overrun with local drop-ins that they risk alienating overnight guests. A recent survey by the Small Luxury Hotels of the World brand revealed that among spa-goers leading dislikes was, "Upon arrival, finding the spa fully booked with locals."

The Wall Street Journal, in a recent article entitled "At Resort Spas, It's Not Your Day, reports that day guests are facing extra fees and minimum expenditures of time and money as well as outright bans at resort spas. The Nob Hill Spa at the Huntington Hotel in San Francisco sets aside all its weekend appointments for hotel guests to avoid crowds that could make the overnight guests uncomfortable. The Ventana Inn in Big Sur, Calif., decided to turn away day visitors after gleaning from customer feedback cards that hotel guests were having a hard time making spa reservations. The Mandarin Oriental in New York has a no day guests on weekends unless they have booked at least a two-hour 'journey."

A study by Hyatt Corporation revealed that overnight guests are far more valuable to a resort property than day guests. Overnight guests who use the spa book an average of 2.1 services and spend about $200 each, compared with day guests, who buy an average of 1.3 treatments and spend roughly $150 each. Spa-using overnight guests also tend to use more of the hotels' other services: They spend 30% to 50% more on meals and drinks than guests who avoid the spa, said Gordon Tareta, Hyatt's director of spa operations.