Yes, it's still working the same way in v6 and v7. It's growing in a size especially if you are using versioning... You can delete the version history (or set the version history to a smaller number) find the example code in the Developers Guide: http://devnet.kentico.com/docs/6_0/devguide/index.html?workflow_advanced_api_examples_versioning.htm
The version history length is applied just to a new attachments, not for those which are already stored in the database. But it's good to set the limit lower to protect it in the future.
However I was solving this issue a few weeks ago with another customer and the solution could be also really simple just to get the size down... because the most space is taken by a binary data of the old attachments. You should be able just to clear that data by SQL command like this...
UPDATE CMS_AttachmentHistory SET AttachmentBinary = NULL WHERE ... your condition to fit your needs (e.g. AttachmentLastModified < DATEADD(month, -1, GetDate()) ... for all attachments older than 1 month)
I hope this will help you.