Since there was no prohibition in Genesis against eating from the Tree of Life, we can only assume that Adam and Eve had, at least at one point, eaten from its glorious fruit. And we have to assume that its life-giving deliciousness was meant to be consumed regularly in order to reap its benefit.
If this is true of the Tree of Life, it must also be true, mustn't it, of the Tree of the Knowledge of Good and Evil. And therein lies an interesting conundrum:
If Adam and Eve simply stopped eating the sinful fruit, could they have gone back to a state of unknowing and therefore, pure worship?
There are several considerations at play here. First, of course, is the question of how much a person can ever truly forget. It is possible that they could have completely forgotten the knowledge of good and evil and returned to a state where their eating of that tree (or not) would have been pure obedience once more. But human experience tells us there is always this lingering hint of a whisper that, "I used to know that...." or "I used to be so sure about...." So there is a part of us that must confess that the unknowing might have eaten at Adam and Eve's consciousness just as much as they had eaten on the fruit, and it may have drawn them back to the forbidden tree again and again, purely out of the fear and discomfort of unknowing.
Which, surely, is an evil in itself and one they would only know by having eaten of the tree. So is it possible that they would forget the displeasure even of unknowing? It's hard to say.
At the same time, they have eaten a fruit which gives them all knowledge of good and evil, which means - they know fully now what it means to eat this fruit. They are completely aware of its consequences. They are also, probably, completely aware of how it works - that they must continue to eat from this tree in order to retain this knowledge. Therefore, having eaten the fruit once, they are now conscious of their need to continue to eat the fruit in order to maintain its benefits.
(It must also be said that they would have become fully aware of the Tree of Life and its benefits and, if it had been a one-bite-takes-all sort of fruit, would not the completely-aware Adam and Eve, in the very face of death, have gone immediately to chow down and thus prevent their inevitable end? This lends further to the argument that it was a tree meant to be feasted from routinely, rather than simply once.)
On the other hand, they have eaten a fruit which gives them all knowledge of good and evil, which means - they know fully now what it means to eat this fruit. (Yes, that is an exact repeat of the above sentence.) But perhaps they do not like all that they have come to know. Maybe the burden of this knowledge is too great for them. Perhaps, even, they have understood now how their knowing negatively impacts their relationship with God. Perhaps, given the opportunity, they would not eat the fruit again, for they would not want this heavy weight it has brought upon them.
Of course, once the knowledge of that first sinful bite wears off, would they remember how much they were troubled by this knowledge? Once again, we have walked into a conundrum for which there is no easy answer.
And where does this all leave God? Here he stands face-to-face with His creation, a creation that has directly defied the one rule He's given them. He knows that in their hearts, this could go one of two ways - they could fall in love with the knowledge that they have and therefore continue to eat from the tree (and also, the Tree of Life), and then there would be nothing He could do to get them back. Conversely, they could be so burdened by the knowledge that they vow never to eat from that tree again, only to forget the burden (and the vow) when the effects of the fruit wear off and eventually sin all over again, only to experience heartbreak after heartbreak after heartbreak as they come to this same place again and again and again.
So the only thing a loving God can possibly do is to remove the temptation altogether. The only possible choice that God has is to say, "I cannot tolerate either your heartbreak or mine, so I'm giving you another place, and I will figure out another way." Thus sets in motion the Messiah, the Christ, the redemption.
And thus sets in motion man's forgetting all the knowledge that he ever had. Unable any more to eat from the tree, it doesn't take long before we see man fall into a place where he no longer knows what is good, what is evil, what is right, what is wrong....