As with most things in life, it's not that siimple. Does someone with a lot of posts have more knowledge? Does someone who found the website five years ago as opposed to six months ago know more? I've been around here long enough to discover a number of members who know a great deal about various subjects discussed on these forums. When I see their names, I pay pretty close attention. However, I do try to rkeep an open mind when reading the posts of any member. Nonetheless, after about 40 or 50 posts, you begin see whether a member's postings are worth seeking out or, as in a few cases, maybe avoiding.
FWIW, let's not judge a member by the number of posts or the year the member joined, but on the content of that member's posts.