In real time applications, IH will grow in huge numbers. Example in my application it has about 180+ million in just 6 months in Production. So leaving it long would drastically effect performance. So archiving/purging this table is very important and you can work with your database admins to set up jobs on the database to do this activity.
The reason behind the purging of Pr_Data_IH_Fact is that interaction history tables contain transactional data which may grow fast.
Therefore this table size increases very fast as a result sql query takes time to execute on this table sometimes it causes slowness or performance degrade of the application. So data older than one month should be purged from this table.