You need to post at least one post per month on average, which means that you can post more in some months and less in others, as long as your total number of posts is not smaller than the number of months since you joined. So after six months, for example, you should have posted at least 6 posts.
You can build up a "credit" in advance to guard against times when you may not be able to post. So if you post 3 messages in your first month, your account is safe for 3 months. Each month, M. Delcamp closes those accounts where the number of messages is less than the number of months since the member joined. Those members will be able to rejoin the forum, but will need to start again with zero messages.
Classical Guitar Forum.
"Experience is something you don't get until just after you need it." - Steven Wright