Thread Inactivity Duration (Indefinite/Infinite)

It's currently impossible to set a thread's duration (Hide After Inactivity, etc) to infinite (indefinite, etc).

I'd like to have the ability to set the thread to never "expire" (be hidden, locked, etc). This could be a role permission if there is concern for community abuse!

This would reduce the number of similar threads opened, as well as prevent certain threads which should always remain open (e.g. help, feedback, or similar) from falling victim to slow communities, as well as prevent more burden on community owners that must post in their own threads to keep them alive.