I had to think about this for a bit to decide how to respond with my own $.02 worth of opinion. I have to say that I can see both sides of this debate. So here goes another "book" of explanation - sorry for the length!
If we were discussing a cat or dog, I would totally agree with those who hate the idea of trading, or finding a new home, for a pet for no "real" reason of pressing need. I have seen so many craigslist ads for adult (or even senior) dogs and cats for free because of what I consider frivolous excuses, that I hate to even look through the ads. It sometimes brings tears to my eyes to think of their fate, and their feelings of loss.
BUT - as much as I love herps, I do feel differently about them than companion animals such as cats and dogs. I feel that cats and dogs (and birds, and maybe a few other pets) often form an emotional bond with their owners, and suffer emotional distress when forced to move to a new home, even if it is physically better than their old home. But I don't feel (based on years of observation) that herps generally form that kind of bond. It is my opinion that a herp (even those that seem more capable of emotion than snakes appear to show) will be happiest when their physical needs are met with proper housing, food, temps, and other environmental requirements. I think that they will not suffer emotionally such as a cat or dog would (as long as those physical needs are met) after a separation from a long term owner.
So logically, I feel no regret if I thin out retired breeder snakes, or those that no longer fit my breeding needs, as long as their new home seems to be at least as good as what I can provide. I view herps as beautiful creatures to enjoy, but I am not bonded to them in the same way as I am to my cats. I can't imagine ever giving up one of my cats. And I do believe my cats would miss me, but my snakes would not. So I have no problem with somebody else trading or selling a pet snake to a good home, for whatever reason they want to do so.
OTOH, I do realize that many people here may feel a bond to their pet snake that may be as strong as what I feel for my cats. I think that is great, and I respect their feelings. But I think that if those people who feel that way think about the debate logically, they would have to agree that the snake may not feel the same bond as they do, and that their snake is not likely to miss them if it goes to a good home.
So, although I would caution a beginner to think twice about thinning out a long term, healthy pet (you may not like the new baby as well as the old, established one, and it may have more problems, too), I don't feel there is a moral obligation to keep it for life in the same way I do for a cat or dog.
Just my own opinion based on my own experience, just as others will form theirs based on their own experience.