Does the NIE currently being given on new F1-visas have expiration dates, or it lasts as long as the visa does - provided the pandemic conditions persist?
Validity is 12 months from the date of issue, valid for multiple entries.
That might be the case for H1B etc categories who have to seek NIE approval; and the embassies inform their decision by email; duration of 12 months is in email, the holder needs to carry this proof; approval can be denied and undergo special checks at POE.
For F1 it works differently. It is not asked but given automatically, no proof needs to be carried, is never denied, no special checking at POE etc.
I believe that a student will have the NIE as an F-1 student until the president ends the F-1 NIE (or the reason for even needing the NIE ends).
The restrictions / waivers are not a regulation but are enacted under a presidential proclamation. And they will be ended by presidential proclamation. The F-1 NIE will end the date the president declares it to end.
As an F-1 student, it’s not something for which you apply. The only end date for it is when the president says it ends.