Some users may not want to bill hourly. This should be customizable (in this case most configured prices would reflect credit per interval rather than credit per hour). A minimum time per VM should also be allowed (so that we can bill every minute, but charge minimum 30 minutes if user destroys right away).
Note: we should still check for billing at reasonable intervals, e.g. if user has configured per-minute billing we should only apply charges in aggregate every hour or so.
Some users may not want to bill hourly. This should be customizable (in this case most configured prices would reflect credit per interval rather than credit per hour). A minimum time per VM should also be allowed (so that we can bill every minute, but charge minimum 30 minutes if user destroys right away).
Note: we should still check for billing at reasonable intervals, e.g. if user has configured per-minute billing we should only apply charges in aggregate every hour or so.