This is pretty simple, if we slice it up.
1. High post count over a shorter period represents higher frequency of posting. Either a high quantity of brief posts, or an amazing amount of time dedicated to the forum (which could indicate many things, including many negative things), or both.
2. High post count over a longer period represents sustained involvement in the forum.
3. Low post count over a shorter period represents casual posting, but indicates nothing in terms of how much the member reads or lurks.
4. Low post count over a longer period likely indicates a lurker.
None of these things really mean anything with relation to content or quality. Someone who posts infrequently like Bluewing possesses a high ratio of signal to noise while a more prolific poster like Jack Flak may engage mostly in brief responses. So, one may safely assume that a newer member with a large number of posts is unlikely to be posting with a high degree of information content, though it is certainly possible based on the frequency of posts. Just unlikely.
With regard to questions of social status, I would expect that the more involved you are in the forum, the more status you will have socially, provided you present a convincing case for likability. The extraverted approach to sociability is more scalable in that you are conducting your social intercourse in public and so may necessarily influence people both in the future (as they read in the archives) and in a broadcast fashion to all members at once. More introverted members are likely to engage in their social relationships in a more discreet fashion through PM's, reps, visitor messages, etc. so their impact will necessarily be more limited when posting quality is equivalent.
Anecdotally, before I became a member, I lurked infrequently as a guest for about a year and a half or more. In that time, I became familiar with a few members who posted memorable or informative posts, such as Maverick and Bluewing or The Liquid Laser.