That is likely the presumption for many people. It is in general naïve I'd have to say as your information is kept for a certain amount of time for returns or disputes and longer for archival and reporting purposes.

I don't have data, but I'd veture to guess that most non-account data is stored nearly as long - if not as long - as account data. (I'm thinking primarily of ecommerce applications here. Services like pastebin are quite different.)