In V3, the limit of data you could back up was 2GBs. I don't see the limit in V4. However, in Jon's post below, it claims there are no limits. Of course, that doesn't stipulate if that is per backup or total storage. I know AC keeps them for 30 days.
http://www.amazingcharts.com/ub/ubbthreads.php/topics/13053/Re_V4_Offsite_Backup_issue#Post13053The biggest limiting factor you would face would be the amount of time it would take to back up 15.7 GBs of data. By my calculations, if one had roughly 2MB/sec of upload speed, it would take about 22.5 hours to upload 15.7GBs.
My server backup to an external hard drive takes four hours. The data is approximately twice the size of your backup, but it is transferred at USB2.0 speeds which is 480MB/sec. Of course, there are other factors present, but you can see why the local backup is doable while that online backup isn't.
A solo practitioner will probably produce 45 to 60 MBs of data files per year (this is just a guestimate). Backup compression will reduce this by 1/4. This can be uploaded in just under a minute at the above speeds. So, online backups of AC is probably meant to backup your databases than your imported items. You can and should back up your imported items to tape or external hard drives along with your data files. It is added protection to back up your databases offsite. You can probably recover from losing your imported items (as bad as it would be), but you really can't if you lose all your notes and scheduling, etc. Plus, it is easier to do incremental backups with the imported items than with the databases IMO.
To be honest, if you want to back up your imported items as well, you would probably be better off using one of the many commercial online storage or back up sites such as iBackup. There are some that do storage and some that do backup and many that will do continuous backups. iBackup is a bit pricey but has the most options and is still much cheaper than ACs.
You can find a good jumping off point here
http://online-storage-service-review.toptenreviews.com/and you can Google online storage and online backup and find many more. You could even make a full backup using the backup program with AC and then back up that file to an online storage site. But, you would still be limited by the size of your backup.
Remember, too, that many online storage or backups will charge by the GB of data stored and also by the amount of bandwidth used.
HTH.
