If you plan on using the included JumpBox backup utility this probably isn't a great idea. There are two main reasons for this ... first, the JumpBox backups are FULL backups and not incremental backups, so they can take quite a while to run. The more data you have, the longer it will take and depending on your data, might take longer than the 15 minute interval. Second, while the backup is running, both the application and the admin portal are disabled during the backup. Combining these two, if you have a 15+ minute backup ... that means that its possible that your JumpBox will never be available.

I suggest you look at our backup FAQs on this page:
http://wiki.jumpbox.com/doc/runtime
specifically the one on JumpBox backup limitations. If you decide that these limitations are fine (e.g. your site being unavailable every 15 minutes) then take a look at the "How can I change the time the backups run" question.

If you really want backups that frequently, you should be looking at commercial backup software. In my experience, these types of problems are solved with live replication at both the database and filesystem level. The JumpBoxes do not yet support this type of deployment.

Austin