Automatic Backups

On my sites I’ve set a destination to my Dropbox.
1. Can I use my Dropbox for all Automatic Updates? That would be reasonable. I pay for Dropbox already and have 2000GB of storage. By the way for only $12/month much better pricing than WPMU.
2. As I’ve enabled auto backups, does that mean no scheduled local/Dropbox backups will run anymore?
3. How do I know when my storage with you is rolling over too quickly?