Question: Do you delete inactive/dormant accounts?

Answer: Generally speaking, no.

If you have made a couple of posts on the forum, then chances are that if you leave the account for a few years and come back it will still be there. The only accounts that are generally deleted as a matter of course are those that have never been activated, or those they have never made any posts at all. If an account has made only one post and then never posted again, then it might be deleted after a year or so. Accounts which have clearly been used at some point by making a couple of posts are not deleted.

The exception to this is accounts used to spam/advertise. Spam accounts always have all their posts removed and are then deleted.