What is the key challenge in maintaining the effectiveness of a campaign for a long period of time?

The Ministry of Tourism, under the Government of India, along with Ogilvy India conceptualized the Incredible India campaign in 2002 to position India as a tourist destination by highlighting multiple dimensions, including culture, festivals, history, and natural wonders. There was a noticeable shift of international tourists from developed countries to developing ones, and the objective of this integrated marketing effort in print, television, outdoor, and digital media was to create a distinctive identity for the country. The campaign theme has varied in the years since it was first conceptualized, but it has retained a simple tagline—
“Incredible India.” It has also used the same logo, the tagline with the “I” of India replaced with an exclamation point. The campaign has been a great success; in its first year alone, tourism in the country rose by 16 percent.