When you refer to configuring a new SP for 7 years, the following questions needs to be reviewed:
-Will the data be on the Primary or Secondary Copy?
-If this is a Secondary Copy, you will need decide on Synchronous or Selective Copy?
-Synchronous copy, will retain all data (Full, Incremental & Differential) based on Basic retention, and then you can also setup long-term retention for Fulls.
-Selective Copy, will only consist of Fulls (daily, weekly, monthly and etc), and at the same time you can also setup long-term retention depending on the type of Fulls.
All of the above are considerations that needs to be taken into account when setting up your Storage Policy.