Pirs docking compartment lifetime

I was looking for the ISS future assembly sequence, and got off track looking
at past missions. The Pirs assembly page at:
http://www.nasa.gov/mission_pages/st...ents/pirs.html

states:

The docking compartment's lifetime as part of the Station is five
years.

Since Pirs was docked to the space station on September 16, 2001 it would
appear that this lifetime has already expired.

I wonder why a module was designed with such a short lifetime? I've seen
nothing about it's life being extended, or it's disposal. So what do the ISS
experts on this group have to say about that?

Glen Overby
Twin Cities, MN