The tube-powered Zeniths I had 30+ years ago (trash-day finds) were great, in my opinion. From my K-2739, a 23-inch b&w console from 1963, to my Zenith SC300 19" b&w portable (1969), every Zenith I've ever owned has been trouble-free and worked great from the moment I turned them on after bringing them home. The K2739 Zenith needed all new tubes, but it was worth it, as the first time I switched it on after installing the last new tube, it worked very well. Very nice picture on rabbit ears on all three VHF channels from Cleveland, and even better when I used the attic antenna. The SC300 portable, which I found in the trash in my hometown in 1977, worked well as soon as I plugged it in and turned it on, and continued to do so for a year until the horizontal-output tube went gassy. Couldn't find a replacement, so I put the set in my basement and bought a new Zenith 12" solid-state portable. That little guy lasted me 22 years, worked like a champ all that time, and never once required service! The detent mechanism of the UHF channel selector broke and jammed on one channel as well after a few years, but that's not why I got rid of the TV; in fact, I used it as a computer monitor for about five years after getting my first color set (a Zenith, followed by another varactor-tuned 13-incher of the same make) in the early '80s. I'd still have the 12" b&w today, but when I moved to my apartment in 1999, I kept the set a year, then threw it out. The reason was I already had (and still have) two color sets in the apartment; there is no more room for other TVs, as my place is very small.
Speaking of early RCA TVs with many years on them (as one person mentioned earlier in this thread), I can relate to the PC-board problems these sets would develop after a few years and lots of viewing time. I had a 1964 Sears-Silvertone roundie in the early '70s (you guessed it, another trash day find) which worked quite well after a couple of minor repairs. However, in 1973, I had to replace the video output tube (6AW8). The replacement had a pin that was bent ever so slightly, so I had trouble getting it into the socket. I pressed down on the tube and, about ten seconds later, heard a sickening crunch as the tube socket broke out of the board and fell to the bottom of the set.
I brought out a 1961 Philco b&w 19-inch portable, put it atop the (now ruined) color set, and used it the next two years until I moved back to my hometown. However, when I bought my first new color set in 1979 (again, a solid-state 13" Zenith), I kept my hands out of it. I replaced it with a Zenith 13" varactor-tuned portable some two years later (because I wanted a set with electronic tuning--my first 13" Zenith was still working at the time) and put the first one in the basement. Kept my hands out of the backs of both TVs, as I know next to nothing about solid-state TV repair (like Carmine, I am no TV repair expert; I limited my servicing activities to tube swapping and minor component replacement in my tube-powered sets, and stayed strictly out of the three solid-state sets I owned). As a result, both solid-state color sets ran for years with no problems whatsoever.
I don't have either of those small sets anymore, as they were put out for the trash before I moved.
Too bad, because both sets worked, and well, at the time. However, I had no say in the matter. If anyone wants to know exactly why those two perfectly good sets were discarded, please send me a PM and I'll explain the whole thing.
As far as Thomson-built RCA TV sets are concerned, IMO, they will work trouble-free for years once the OB tuner problems are corrected. My 1999 XL-100, which I purchased new, is a case in point. Had some problems with the tuner in the beginning, but after those were corrected the set gave absolutely no trouble and hasn't yet. I use it a lot, especially in the winter (it's my daily watcher) and like its automatic picture-correction circuits (auto color, black stretch, black lock, etc.) as well. This set has a beautiful picture on cable (antennas don't work well in the small town where I live--too far [45 miles] away from the transmitters of the seven Cleveland TV stations) and works well with my VCR as well. Now that the OB tuner problems have been corrected, this set works every bit as well as my Zeniths (and a few older RCAs I had) ever did. I expect it to last a long time now.
BTW, the CRT issues in the RCAs seem to have been corrected as well. I was looking at some earlier posts here on AK yesterday, and read one from a member who seemed to think that the quality of RCA CRTs actually improved when the company was sold to Thomson. If this is in fact true, I believe it. The dark-tint CRTs in today's RCAs and Zeniths (the latter, when Zenith was still an American company based in Chicago, used these tubes in their Chromacolor II sets of 1970s vintage, but the quality of those tubes went down the drain in a hurry when GS bought out Zenith and moved the company offshore) produce much better pictures (blacker blacks, whiter whites, better colors) than their predecessors with gray or green faceplates. I'd use a dark-tint tube to replace an older one any day in the year, provided the electrical characteristics (and screen sizes, of course) of the tubes were identical.