We also save searches, but again, not in a personally identifiable way, as we do not store IP addresses or unique User agent strings. We use aggregate, non-personal search data to improve things like misspellings.
So it appears that they still save your search terms, but the retention is anonymous. This is a lot better than most search engines, but could it still be a problem if you accidentally paste passwords (especially both the username and password), personal or otherwise sensitive information into the search bar? I’ve done this by accident on more than one occasion.
Could someone provide some more clarification (maybe even someone who works for DuckDuckGo) on how the how long search queries are kept and exactly what “aggregate” means?