There is currently no timer option when locking a trust level; it’s turned on and off on a manual basis.
It’s possible for users to request for their trust level to be locked, if the admin of that forum is happy to do that for them.
Just spotted your edit:
Discourse also has the option to Silence or Suspend a user’s account, if the admin feels it’s necessary. These options do have timers.
You can read more about Locking Trust Levels, Silencing, and Suspending in the:
2 Likes