If the penalty of sin is paid by Jesus, then why do Christians die?

If you've ever engaged with the question of why Christians still have to die if Jesus paid the penalty of sin, the following post at The Gospel Coalition is interesting food for thought and discussion:

http://thegospelcoalition.org/blogs/tgc/2010/07/14/why-do-believers-have-to-die/

Interested in your thoughts ...