In Christian theology,the idea that without the 'entry' of sin?

into 'the garden',Adam and Eve and all the rest of us - and all the animals would never know death . .would in other words LIVE UNTIL INFINITY (!) Surely this is a ridiculous position to take,but there are many - including Milton - who have held this view. Are these people serious? Isn't holding to a theology such as this tantamount to insanity? What lunacy! Live forever! Who else believes this tosh? Because surely this is just mythical nonsense. .