How long should Copyright terms last

Please read the following article: ;http://www.washingtonpost.com/blogs/the-switch/wp/2013/10/25/15-years-ago-congress-kept-mickey-mouse-out-of-the-public-domain-will-they-do-it-again/ . ;

• What reasons are there for having copyright terms last this long? ;What consequences are there to having a long copyright term? ;