If your server still offers the data, it's not likely to be purged. It wold be a good thing to find and fix the common patterns that are creating this issue. Your site may be wasting some ranking power.
[edited by: tedster at 4:16 pm (utc) on Sep 4, 2010]
Google has a very long memory on this particular topic and will likely view this problem as spam.
Just do a cost / benefit for the site. If the cost is too high relative to the benefit, then you're making the right choice. Don't spend time worrying about it and focus your efforts where the rewards are higher.