I've never got into the Trading scene but I've been thinking about that more and more lately. Now I wish I had kept my Lost In Space Season 1 set since someone here might have been interested in making a trade for that one. I think one of the reasons I haven't entered the trading scene is that I've been fortunate to have bought TV/DVD sets that I've wanted to keep in the library, with that one LIS exception. I did watch that entire set but I found that this one didn't hold up as well for me as my other sets. I'm a Time Tunnel fanatic and have the "Voyage...Sea" S1 set so it wasn't an Irwin Allen thing about LIS.
I have loaned out and borrowed a couple of sets and that has worked well for me so far. That's how I watched "Firefly" from a friend's set. Good series but it saved me $$'s since it wasn't enough for me to add it to the collection.
Jeff, that's interesting that you brought up LIS, because I feel much the same way. And it's really the only series I'm that way about--the rest I feel assured about staying in my library long term. Well, OK, maybe if I think a bit about UFO...
At the time I purchased Seasons 1 and 3 of LIS (didn't care enough to buy S2) it was one of the few series in my tv/dvd collection. So I was a bit less selective in my purchasing. But I too find that this series does not hold up as well for me as TT or VTTBOTS. I'm seeing many more technical & production flaws and lapses in logic in this series than I did some 20 or so years ago. It doesn't help that the transfers look rather substandard by TT and VTTBOTS standards, especially in the case of S3.
I've traded a couple of things in the past. I picked up Mr. Show as a blind buy (s1-2) and didn't really care for it that much, so I ended up trading it for some South Park that I knew I'd re-watch a bit more. If you can find some reliable folks to trade with, it can be a great thing to get a new set to watch if you've tired of watching a particular show. I have a number of shows that I'd love to trade for something else at some point, but I haven't sensed much interest in the trading circles at this point.
The only series I'd even consider unloading at this point would be "The Osbournes". It's been years since "2 1/2" was released, and at this point I think it would be highly unlikely that the remainder of the series will be released. This summer would've been a golden opportunity too, with Ozzy's "Black Rain" album just released, and Sharon as one of the judges on "America's Got Talent".
For the most part I've managed to collect shows that are either completed (or near to completion). So besides "The Osbournes" I wouldn't ever consider trading or getting rid of any of my other sets.