[otrs] Auto-Close tickets

We have here an active support team all using OTRS, and people are writing to support every day tens of messages - a lot of them don't answer more than once, and there is no way we can tell to leave the ticket open or to set next ticket state as closed when answering. so is there any way to make the tickets auto-close themselves after a certain period of time ? because now each OTRS agent has a few hundred locked tickets because the customers never continued conversation and we didn't know that they won't. N.