In any data management policy, there are two extremes: save everything (just in case), and delete everything that ages out. The two extremes work hand in hand, as eventually, you decide that even if you want to save it all, the realities of storage costs have forced you to delete your data arbitrarily.
Ideally, you would retain "interesting” data that might be useful and delete the rest. Even better would be to not collect the data in the first place.