Every morning I let my dog out into the back yard and although he recognizes where he is, you'd swear by his excitement that he'd never seen the place before. Each day he seems as if it's a brand new world to him.
To live forever and be happy about it ones sense of the passage of time would have to be altered and ones memory would in some ways have to fail them so that things seemed new again.
Maybe when they talk about Adam and Eve having lost their innocence and their eyes being opened, this is what is what they mean. Maybe (if they truly ever existed) humans were supposed to be more innocent (like my dog) and their concept of time was meant to be different. Maybe our current concept of time and tendency to become bored is part of the "imperfection" we inherited. Maybe our concept of time and the passage of time is all fouled up.
At any rate, it's hard for me to imagine that all those years ago when my parents randomly conceived me that I was intended to live for all eternity just because the sperm that swam the strongest at that moment, was the one that made me instead of one of the other thousand that could have been someone else. If they'd have gone to bed 10 minutes sooner or 10 minutes later I wouldn't even be here.
Maybe wanting to live forever is part of the human tendency to be greedy or to be self absorbed. We always want more, even when sometimes more would be the worst thing ever.