bdd yeah it just inherits the same base settings for all backups from what I remember, nothing separate just for S3.
There's feature requests to add more options for backups, but backups as a whole are getting a lot of attention just to get them stabilized and debugged - doubt new features will be made available for some time.
Theres some items for S3 in the roadmap "planned" section, to make them incremental. Maybe that will get some action by the end of the year.
I think the backup interval is getting worked on now, since it's been reported that the interval selector doesn't work currently and backups just run whenever.
