This was all covered, re-covered, summed & re-summed by page 10 of this thread. I see no point in reposting what I've already written. I also find it more than passing strange that you see twist and turns where there has been but one unified message. The conclusion is that you are misinterpreting a great deal of what I say and reinterpreting it into what you want to hear, thus providing your own bifurcation in all but the places where I have achieved unambiguity. There are no mixed signals.
"quitting when ahead" is completely and utterly illogical since the only word in the phrase that is used correctly is "when".
People that "'quit' when they are 'ahead'" do not actually "quit" and they don't do it when they are actually "ahead".
If one removes the multiple quotes, it's just bad English. What these people are really saying is:
If I discard all previous results (for no other reason other than I went home and slept in my own bed and because I want to) and only look at how I've done during this completely arbitrary time span, I'm going to take a short break, because during this period of time I have experienced positive fluctuation, which reduces my lifetime losses and that I'm going to define as "winning" because I want to. I am neither truly ahead, nor do I intend to truly quit, but I'm going to disregard all logic and do something that my dysfunctional brain can use to convince myself I don't have a problem...and since this will result in me gambling slightly less, everyone (including myself, who really needs convincing) will hopefully agree that it isn't a bad idea.
Is that clear enough?
If "quitting" when you are "ahead" has any place, it is as a stop-gap-measure-jury-rigged-band-aid for people with potential or current gambling problems.
In order for it to be a good idea, you would have to have current or potential gambling problems, and in that event I cannot say that it wouldn't be a GREAT idea!
If you really need a reason to leave the casino, go for it. Just the fact that you would consider such things, probably means you shouldn't be in a casino at all.
This practice and its associated illogical thinking is one of the primary methods by which "recreational" gamblers add "fun" to a net negative experience to relieve their cognitive dissonance though the use of illusory control. Unfortunately, for these people the practice may increase their potential to develop gambling problems later, as the practice comes with a host of biases and cognitive distortions required for it to make sense to them. It's basically like someone that hallucinates a guardian angel to help them make it though a blizzard and reach home...super useful during the blizzard, perhaps not so great when the Angel keeps speaking to them during their normal daily life and they get locked up for schizophrenia.
Therefore, I can only recommend the practice for people who already have, or are in the process of developing gambling problems...and even then, only if all other methods of terminating or reducing their play have failed.
~FK
P.S. I think it might possibly have a place in the treatment of hopeless addicted gamblers. The medical community merely thinks of it as a risk factor for pathological gambling or as a sign you already qualify as a problem gambler.