Digital BW, The Print

I have been having huge problems with Lyson small gamut inks shifting 
from sepia to greenish hue in a matter of months. These are prints 
that are both framed and sealed under glass in low-humidity,
primarily 
incandescent light settings, and also prints simply stored in a 
drawer. They are printed on Hahnemule Cotton Rag paper, and sprayed 
with coats of Lyson Print Guard. In other words, you couldn't do 
everything more right if you tried. 

I have called Lyson in the US and the UK and both technical 
departments say that they have never had anyone call about this 
problem before. And yet in limited reearch, I have already
encountered 
a few other people with the same problem. Lyson have all along 
adamantly maintained that their inks have an archival value of 70 
years. To me, this is clearly irresponsible, inaccurate marketing, to 
say the least. 

So my question is...is there anyone out there having the same 
problems............