Congress enacted the termination provisions in order to give an “author a second chance to control and benefit from his work" and to "secure to the author's family the opportunity to exploit the work if the author died", according to Stewart v Abend, 495 U.S. 207, 218 (1990).
Shourin has launched an online calculator and website to enable readers to evaluate the rights and risks associated with the termination of copyright grants. While the termination provisions are regrettably intricate, this online calculator seeks to people through the basic issues and maths necessary to figure out when an author may terminate a grant. It does not cover all of the contingencies needed to make an evaluation, but seeks at least to provide a useful starting-point.
I thank Shourin for drawing this to my attention and would be interested to hear from any readers who put the calculator through its paces -- or, better still, who would like to review it.