It would be useful for storage budgeting needs if LS used the free space value and provided a % of change over time. Maybe nothing fancy but put it on asset pages what % disk usage has increased or decreased over a defined period of time. If the period of time could be customized that would be even better, 7 days, 30 days, 1 day, etc... If it did that it would be simple to build reports based on the data.
This feature is on our customer wish list, but we do not currently have a release date for it. The suggested "workaround" for now is that you have disk reports sent on a scheduled basis, so you can manually track changes.