I have been using AC in FP office for over 4 years. We have over 30GB of data in Imported Items. It takes 3 days to upload to AC, so I back up AC without Imported Items then I use Backup Assist to store an image of the imported items folder. It runs this automatically every night.
30GB?! That would take 7-8 days on a standard DSL line. I'd probably just keep a folder synced on an external drive. Services like Carbonite/Backblaze have incremental backup and my database in the normal ENC file to be backed up.