It is not a question of time, rather a question of how much effort you put in. Waiting for a domain to age will not make its PR go up. To get more traffic and a higher PR, i would try the steps below: 1) Write quality articles and submit to article directories 2) Get QUALITY backlinks from other high PR websites. The quality is important as otherwise, you could get penalised by google. 3) Guest blog on a popular site to get more "referral traffic". 4) Use meta tags once you are paying for your hosting - improves SERP and general PR. 5) Use social media - rather self-explanatory. Check out my multi-author website, promoteyoursites.net for more info on SEO, advertising campaigns, link building, and generating more traffic.
If you're referring to toolbar PR, that currently updates about every 3 months with the next one due in early February. Google doesn't always maintain PR updating scheduled consistently though. Technically if you get enough links with PR before an update your PR should increase. Getting search engine rankings is another story. That can take a long time depending on how competitive the keywords are and what kind of effort you can put into it. There is not really a set amount of time.
Google page rank depends upon how much back links you got from high PR sites of your same niche. But back links should be created in a ethical way. If you create many back links in a short period it counted as a spamming technique. There is no time frame to get your PR but you will get page rank quickly if you work with the guide lines of Google.
Yes Mikepetersen, you are right, Page Rank depends on our work, Do quality work if you want Page Rank.
It takes approximately 3 to 6 months to get page rank. You have to do SEO(quality link building) steadily without spamming to get a good page rank.