In point of fact the length of protection of copyright changes over time. And for a good part of the last century the period has been extending faster than time goes by.

Should this continue then pro-copyright pressure groups shall truly circumvent the US Constitution's statement that copyright shall be for limited terms by making the term of protection "forever minus a day".

An interesting question for the lawyers therefore arises if you borrow code examples from this site. Legally the copyright is clear, you need permission to use it in your own code. But practically...people wouldn't post if they were going to object to your using it!