Digital textile printing with Dupont inks onto natural fabrics
I don't know about the inks your referring to specifically but given your concern about too much fading, you may want to consider pre-treating your fabric and being done with it, esp. if you don't trust your print shop or its very important it is to my customer that the design not fade.  My perspective is more of from that of a professional artist/craftsman working on a project, although I would want to spend as little as possible, I would need to weigh the cost of doing it once well against the cost of having to redo something that didn't work out.  I hope this helps.