I'm not even sure we can extrapolate that the NSA is storing anything like every text message long-term (as opposed to metadata, or samples, or the full transcripts of individuals targeted for investigation, or a machine learning trained weights set to flag messages that indicate someone should go on the targeted-for-investigation list).

6 billion text messages are sent per day in the US. That's about the volume of Google web searches, and I know from experience Google doesn't have the capacity to log every search or the logs of evaluation of every search. If Google lacks the capacity, I suspect the NSA lacks the capacity.