Harvest Now Decrypt Later principle holds very well for intelligence work, the harvested information could be useful for very long time.

You can see this in the long time intervals specified for Declassification of classified documents.

"Executive Order 13526 establishes the mechanisms for most declassifications, within the laws passed by Congress.[1] The originating agency assigns a declassification date, by default 25 years. After 25 years, declassification review is automatic with nine narrow exceptions that allow information to remain as classified. At 50 years, there are two exceptions, and classifications beyond 75 years require special permission."

https://en.wikipedia.org/wiki/Declassification#United_States

"Decrypt Later" should generalized to "Use Later", many recordings are useful without decryption, just from the metadata you can establish who, when communicated. Identification of relations between persons, building of social graphs, is the basic of intelligence work. Much of this relationship analysis can be done just from metadata.

One example of such analysis is the NSA Co-Travel Analytics

"CO-TRAVELER does not simply collect location information. It creates a portrait of travel times and people who crossed paths, revealing our physical interactions and relationships. The cell site information goes beyond email and phone calls and ordinary telephony data, allowing the U.S. government to know who we are with in-person and where. This is information that would be impossible to collect using traditional law enforcement methods. "

https://www.eff.org/deeplinks/2013/12/meet-co-traveler-nsas-...

https://www.eff.org/files/2013/12/11/20131210-wapo-cotravele...

Well put; the scope of usefulness of surveilance data lies well beyond what is in that data itself, but how it relates to other data. You don't necessarily need to decrypt data to distill value from it, as its metadata (location, datetime, medium, etc.) is also (and potentially more) useful when related with other metadata. Storing this data is also a monumental task, given the fidelity of records that many consumer devices create, store, and upload.