Originally Posted by StarkReality

Duplicate content penalties are not related to the age of duplicate content, so if you already suffer from a penalty or got huge ammounts of DC on your blog, removing it is the safest way...although I'd leave it as it is and start a new blog instead.

Many people tend to spend loads of time fixing sites. If it's a big established site, it's worth the time...but more often forgetting about it, enjoying the traffic that's left, penalty or not, and starting something new works out much better.

Btw, feeds are no problem, you just need to rewrite them. Nothing beats writing all posts yourself, but it's time consuming and can only be done for a few selected sites.