It will depend a lot of factor...If you get good page rank..You cannot maintain the page rank of any website forever...
Its my lunderstanding that you need to keep building backlinks untill you get to a high PR, somware around 5 or 6
Increase the number of your sites's backlinks. For this u can use directory submissions, social bookmarking submission, forums, blog commenting, and article submission.
Change of Page Rank is because of Google changing its searching algorithm and crawling strategy. To maintain the page rank,you have to produce very conceptual content on your website and it should be unique.And for increase your page rank,you have to get back-links from very high PR site for which ,mostly people are using link exchange activity.
If your websites already have a PR1 or higher, you should try with VoltRank.com.... it is a very powerful and free tool.
You know there is post like this everywhere on this forum. The problem is that google is catching wind of every SEO trick that people use and tries to make them less effective. In my opinion thats wrong on their part. The harder you try to plug a loophole the more loopholes people will find.
High quality and relevant backlinks along with frequently updated user-friendly and keywords enriched contents on site would help increase and maintain pagerank.
I Think you have to do High PR Directory submission and Forum Posting, Blog Post. and also do updated content and good backlinks. SEO Analyst
directory submissions, articles submissions, social bookmarking,Press release and do some high page ranks links building ....