SharePoint Dragons

• If the historical data doesn’t take up much space, leave it in the original list.
• Turn on versioning if you want to track the history of individual list items.
• If the history involves different records, leave them in the list and sort the view on the date of the history with the most recent at the top.

Finally, the most common option: eventually archive the items to a different site collection in a different content database.

Follow the ongoing Wiki effort to discuss the best practices regarding this topic at:
http://social.technet.microsoft.com/wiki/contents/articles/7999.sharepoint-2010-strategies-for-handling-historical-data-in-custom-lists.aspx