Digital BW, The Print

A question for the legally knowledgeable:

Someone mentioned that Epson has to sue to keep their patents alive,  
otherwise a competitor like HP could come along and capitalize on  
their technology and prevail based on Epson's failure to get active  
and raise the issue.  Couldn't that same argument pertain to protect  
artists who have been using the cart technology for a number of years  
now?  When did Cone's Piezo system first come out?  More than ten  
years ago?  Granted, those carts weren't chipped.  But artists have  
established themselves and are making livelihoods using this  
technology having nothing to do with cart type or anything else other  
than ink different from or superior to anything Epson offered at the  
time, or even now.  Did Epson spring into action in a timely fashion  
and say wait a minute; you can't use those carts/materials?  Or did  
respectable and valuable businesses and artists become established  
for years, now to find their livelihoods and art threatened?   
Couldn't some case be made based on the length of time these  
practitioners have had, and based on the inherent value of what they do?

James