Digital BW, The Print

Last week I looked through my digital prints dating from 
1994. The first were made with a Star thermal printer, the SJ144.
NO problems  there except the low resolution. Next an Epson which 
faded so quiuckly that I  sold it immediately.Then a better Star, 
whose 
prints faded while they were on display in a local gallery, to my 
great shame. I then gave up trying for some years. However in 1999
I resumed my efforts with a HP Deskjet 970c. Some of those prints are 
still perfectly all right, especially those made on ordinary 80gsm
copier paper. Following recommendations from another photographer,
I bought a secondhand Epson 800. This time I tried supposedly-
archival Lyson Small Gamust inks: the prints loked really nice.
Especially those on Epson Glossy paper. The colours they are now vary 
from purplish to reddish to greenish.
Finally, I got a refurbished Epson 870, in August 2002. I liked the
results but will they change colour or fade? I haven't used this
printer for B/W - only with the original inks.
I must add that I still have some chemically-processed prints
which I made in the 1960s,and they are O.K.
My question is: how old is the oldest digital print which is still
in reasonable condition? What printer and inks and paper were used
and how was it stored? I'll be grateful for any replies.