Instead on just focusing on the raw quantity of posts, maybe there's a more meaningful way of looking at it.
Let's use the Top 100 Posters as our foundation. If you're not in the Top 100, you're not posting enough. We can then work from there.
The Top 100's lowest is 37 posts. If you have less than 37 posts, you're not a mainstream member. 37 posts is not too hard to get, so the Top 100 sounds pretty reasonable enough.
Usually, wealth is divided into 5 Blocks. Meaning that if you make about $96,000 US per year (about $113,000 CDN), you are in the same category as Bill Gates.
(edit: Therefore we can use that analogy to describe our post counts, dividing them into 5 appropriate blocks, substituting post counts for amounts of money, as shown below)
To be on the 1st Block, you need 730 posts
To be on the 2nd Block, you need 323 posts
To be on the 3rd Block, you need 120 posts
To be on the 4th Block, you need 55 posts
To be on the 5th Block, you need 38 posts
The most important thing to celebrate is to go from one block to another (going from block 5 to block 4, 4 to 3, 3 to 2, and 2 to 1).
I just barely started to enter the 3rd block, and got a long way to go before I make it to the 2nd block. For TSM/Dogbreath and the others in the 1st Block, enjoy and celebrate!
edit: Fixed the error which implied that Larry was in the same financial category as Mr. Microsoft himself