Help us taking care of our guardians ;)
Do you mean in the scanner, when looking at the collection of portal keys currently in your inventory?
@Perringaiden previously suggested that capture dates be added back to intel: https://community.ingress.com/en/discussion/8268/feature-request-capture-date-on-intel
Theres no Guardian anymore, and that data would just bring back the same problem as before.
I just like 991 days in my profile summary ;)
Sorting by portal age would help me keeping that number growing.
I pretty sure you already know which portal it is.
But would be nice if it's shown only to the owner, like showing last time the portal was captured by me, not a public data.
Honestly - I don't. After three years I have only few candidates... :)
The knowledge of the portal age should be of course restrictly private thing.