As much as death is painful

Well the mind does seem to decay with age and the ability to learn new things is diminished so it would seem you would hit some stage where you either become a baby in an old body but without the ability to learn because of degenerative brain diseases or you would be yourself but stuck at a level of brain "saturation" where all the possible neural connections would be made and that's it nothing new would ever happen again so that would be kind of hellish wouldn't it? Death comes to spare us of that i think. Pretty necessary.