Do Bank Robbery bosses disappear after a certain time?

Question

Most nemesis bosses disappear after a while. I would like to know if the same happens with the Bank Robbery bosses (Jesse the Wicked, Mornenion, Elvira the Hammerthrust and Robby the Reckless).

If so, how long does it take for them to disappear? And what happens to the bank that was robbed? Does it remain closed until the next server save?

Answer 1

Today my friend found Elvira the Hammerthrust on the test server. He lured her away and left her alive. After more than 10 hours I decided to check if she was still there and, yes, she was. So, answering my own question, most likely none of these bosses despawn.