I'm sure you already know this, but the purpose of modern copyright/patent law is to provide incentive to invest the time and money to create original inventions. You are rewarded by receiving an artificial monopoly for a period of time to let you recoup and profit off your time, money, effort and ingenuity. If the time period is too short, this stifles innovation as there is no profit in it. If the time period is too long, this stifles innovation as once you create something, there is little incentive to create something else; and it prevents others from improving upon your designs.
In the realm of patents, consider Kodak who to a large extent created digital photography. However they did not do anything with their patents for nearly 20 years, their initial offerings were sub-par - and at that point when the patents expired their competitors stepped in, innovated and outperformed; and now every man
and his dog has a digital camera. Imagine if Kodak were able to keep their patents on digital photography indefinitely (infinitely?).
We are living in an age where we refer to artists and authors as 'content creators'. Anyone can produce from their own basement and market to the world, and the cost of doing so is essentially free. Because of the volume, ease and low cost of content creation I firmly believe that copyright laws in their current form are outdated, and at the very least the duration needs to be drastically shortened by at least half.