let's say there is a page about "healthy apples". The page is not successful, has no backlinks/PR, doesn't rank at Google and the topic is not so important for me any more. Therefore I want change it in "apple juice".
I'd like to change also the URL, i.e., creating a complete new page, reflecting the new content ---> .../apple-juice
The old page/URL would vanish.
Is it worth to keep the old URL, because it may have collected some positive user signals (Panda) and age (4 years) or anything else which I would throw away?
What would you do?