Another GE question

[zenithfan1]

I know theres been a plague of the Porta-Colors lately but I have one more question regarding the General. I have 4 GEs, a '72 19" 18CD, '73 Porta-Color 10HD, '74 Porta-Color 10HE, and a '75 19" 19CD. All of these came from very different places and were not taken care of until I found them. My question is: How come these supposed cheap, economy, not-supposed-to-last TVs have almost if not all of their original tubes, including the HOT? Some of these are obviously high hour sets. Yet every tube inside has the date code of when the set was made. Were the GEs easy on tubes or did the General just make really good tubes?