You might be surprised to discover that a 40 year old life is fairly standard in nuclear power plants[1], in fact some countries hope to keep their plants active for closer to 60 years. At close to $7B+ investment in just the building phase of a modern nuclear plant and close to 7-10 years construction time per plant[2], the limited lifetime of the plant does start to become a concern in the financial sense though.

[1]: http://www.iaea.org/newscenter/news/2007/npp_extension.html [2]: http://en.wikipedia.org/wiki/European_Pressurized_Reactor