Does it have to be a continuous process even if there isn't much competition for the keyword? Thanks for the info but I believe these keywords you rank for doesn't have much competition correct? This is the case for me as well but I think the other replies were based on competitive keywords, in which case I think you'd have to keep link building to stay on top. Or are these keywords you rank for competitive as well? Luke
Don't stop making links, otherwise you will see a sudden fall in your position. Actually Page rank is the main key to boost and make stay your website in search engines.
Lol, I got a new word today in my dictionary "continuousness" BTW you are right and OP just try out and stop building backlinks for your site for a week or two and you will see the results by yourself. Google will never penalize you for not building your backlinks or stopping them all of a sudden .. Instead your rankings will step down to page 2 and page 3 and eventually in 10s and 20s if you stop doing what you are doing right now or slower the process