Put a link estimator on this page http://www.4th-media.com/link_building/ It estimates how long and how many links needed to get to top 10 according to 1) site age, 2) current ranking 3) keyword competition The estimate is based on the data we've worked on over 200 sites and thousands of keywords. Welcome to play and give feedback.
The estimate is reasonably accurate. The proof is the results from thousands of keywords and hundreds of sites we've worked.