Having 5,000 posts means absolutely nothing. The contribution and importance of a member is based on the way that member writes, on the quality of that member's writings' content, on that member's interventions for the forum's wellbeing. These can be noticeable from nearly any post, even in the writing style and way of expression.
For example, you can have pretty coherent members with a high degree of proper written expression and with coherent posts that have no more than 100 posts while you can see mattabestian nonsensical floods.
I advocate for archiving all kinds of posts even if a silly kid will get 4,000 posts 90% of which are legible garbage.