Do Shared-Links "expire", even without a specific Date set?

I have a request from a User who has created and send a Link over a Year ago, claiming the Link was now invalid even though she changed or deleted nothing.

I did update NC in the meantime with two major Versions, so my qquestions are:

  1. Do shared Links stay the same or can they change due to NC-Upgrades, f.e. from NC v18 to 20?
  2. Is there a general expiry-date for Links, f.e. after 12 Months?