Digital BW, The Print

I was just reading these tests of piezo inks 
(http://www.livick.com/method/inkjet/pg2K.htm) and was wondering if 
anyone here is concerned about using the portfolio black ink?  I
think I read on the inkjetmall website that over time it should fade 
to the approximate density of museum black but these tests makes it 
look much worse.  Any thoughts?

Jenny