Please don't delete them all
30 days is a short time. Your board's default is set up to display messages posted within the past 45 days. It is also set to display messages posted within the past year, if one checks the box to see those older messages (or even ALL messages ever posted, if one wishes to see them). In some cases, a topic is very interesting, and should be retained. I'd also like to see Board of Enquiry messages kept for at least a year, if not permanently.
By deleting them all so quickly, you may be depriving us of reference material that we find useful, even if we are no longer posting on that topic. I must say that there are posts for which deletion is applicable, but I do ask that you use some dicretion, and not make it a hard-and-fast rule.
"Nothing is so firmly believed as that which we do not know."
<i>H. L. Mencken</i>