Insided can verify, but I think things that are trashed - topics, replies - are still hanging out in the moderation console, under trash can. There’s a “restore” option in the top drop down. 

Hi! It is true, once a topic is trashed it is still listed in the trash can and will not be removed, unless you select and permanently remove the content there. So there is no set time after which trashed content is permanently removed.

Same goes for replies, if you trash them they will still be listed in the topic moderation page in the control environment and not be deleted.

This way you can always revert it or read it back should that become necessary. I personally hardly delete content permanently, unless it is something else that has absolutely no value.

Good to know! thank you!