Ranking the website of a (long term) client?

I have a SEO client for who I've been working for almost a year now.

I used a broad mix of links like the packages (web 2.0, social bookmarks, profiles, social signals,...) you can find in the Buy&Sell of the forum + article links from local high PR domains.

What can I do more to rank the chosen keywords?
I don't want to overoptimize the anchors and also want to avoid a penalty.

How do you handle long term SEO clients?
Any suggestions or tips?
Is 'hiring' links from networks a good idea?

I have been suggesting my clients for the Trie1 strategy leaving footprints.

I wouldn't suggest you use network links. Since you plan it as a long time project, the networks can be shut down anytime. Try to diversify anchor text as much as you can. Check WM Tools for new search terms that the site is getting visits from and optimize them too.