Use of attachments in Oracle eBusiness suite - what are the implications for storage and archiving?

We are looking to use attachments in various applications - iExpense, GL Journals and Purchasing specifically - and need to assess the possible impact this will have on performance and storage / archiving. 

Can anyone share their experiences or is there any documentation or white papers that can shed any light on this?  Are there size limitations or guidelines on attachment size?  Security issues with access to viewing attachments?  How do we purge the attachments on old transactions?

Any help would be appreciated.