Pork. The Other White…oh, wait

I heard on the radio recently that the National Pork Board has implemented a five year strategic plan that among other things, calls for a new slogan.  There’s going to be transitional advertising until March 2011 when the new brand materials will be unveiled.
My initial reaction was, why?
If there is anyone out there who hasn’t heard, “the other white meat,” I’d sure like to meet him.  The slogan is 23 years old and widely recognized.  And this statement, from the website of the National Pork Board, demonstrates that they recognize the equity of the slogan:
“We know for certain that we will protect the Other White Meat’s important heritage both in marketing and legally.”
So, why change it?  When a tagline enjoys such recognition and equity, what creates the feeling that you have to start over with a new one? I did a little research to find other slogans that have been in use a long time and remain effective, even despite longevity. Here are ten popular tags (some still in use, some not), followed by the company and date which they were first used.  Do the age of any of these surprise you?
Just Do It. – Nike 1988
Like a good neighbor, State Farm is there. – State Farm Insurance 1971
It’s the real thing. – Coca Cola 1969
Because I’m worth it.  – L’Oréal 1967
Finger lickin’ good. – KFC 1952
The milk chocolate melts in your mouth, not in your hand.  – M&Ms 1954
Diamonds are Forever. – DeBeers 1948
Snap! Crackle! Pop! – Kellogg’s Rice Krispies 1932
Good to the last drop. – Maxwell House 1915
When it rains, it pours! – Morton Salt 1911