Obviously, your brand can't stay new forever. All businesses have to change their slogan or brand at some point, even if it merely means adding something simple to it. In all cases, however, audience research is important. If you don't know what your audience wants, you won't succeed. If you don't test your new product or slogan or whatever it is on your audience, you have less of a chance of succeeding.
Research doesn't always work, as evidenced by Coca Cola's change in flavor, which tested well but didn't make it on the market. I'll write more about Coke in another post. You can't always completely depend on your research, either. Planters peanuts asked consumers what they'd like to see added to their Mr. Peanut mascot, and the number one answer was that no addition was needed. Some times the old still works. People like classics.
Planters went ahead with a major change, however, adding more clothes and a new voice to the character, as well as turning him into a computer-animated character. The voice, provided by Robert Downey Jr., may attract Downey's fans, but it doesn't fit the upper-class English accent associated with the character. The new commercial, itself, is funny, but you have to wonder how it will go over with the public. Personally, I like it, but we'll have to wait and see if it succeeds or not.