My primary suggestion would be to focus on the strengths of this type of format, which would be it is easy to find stuff that was posted longer ago and keep adding to that. Many of us are on the Facebook Budget rock group where you can yammer about a record for a day or two and then never need to reference that discussion again. It's just mindless drivel. A forum like this should be more of a longer term record.
Where this would be the most helpful is in the Travel section where there could be long running locally specific threads about record stores, book stores, clubs, restaurants, arthouse cinemas, or whatever in any city and you can just find the Lexington, El Paso, Phoenix, or whatever thread and it is all right there.