How long your files are kept
Your order history is permanent; the files move to slower storage after 90 days.
Your order records — what was ordered, when, for how much, and every message on it — are kept indefinitely. Nothing about your history is deleted.
The files themselves
For 90 days after an order closes, its files stay in instant storage and download immediately. After that they move to archival storage, which costs a fraction as much to hold. They are still yours and still retrievable — retrieval just is not instantaneous.
If you expect to need a case again — a remake, a second stage, a medico-legal record — download the files while the order is fresh and keep your own copy. That is good practice regardless of how we store them.