Bumping old posts with something like "How is this going now?" does nothing. The page is already indexed and the new content has no seo value as far as the keywords are concerned. Now if you add some keywords in there then things change a little because of the added content.
All the congrats and thanks posts do nothing except to keep it on the front page of the forum. The actual value of links from forums is still being debated but people that did nothing but links from forums have seen a drop in their rankings or some have even dropped out of the top 1k.
The key to this thread is in the first post.
If you want help, you have to ask a question. One thing that you need to do is diversify your links.
Articles, .edu, .gov, Wiki pages, blog comments, micro blogs, doc sharing sites, etc.
This way if one get devalued such as the forum profiles and blog commenting seem to have been with the recent update, you don't drop off the radar. You also need to spread it around to as many domains as you can. Use your keywords as anchor text whenever possible.
It does take a lot of time and effort to find all these though.