An interesting story here of a man who, starting at the age of 58, has pretty accurately memorised the whole of Paradise Lost (a mere 10,565 lines.) He's now 74 and still got it on (in?) his brain.
Do such amazing feats of memory training help your general cognitive abilities though? Apparently not:
So I guess some mornings he still can't find his car keys, but at least he can recite line 8,576 of a poem while he's looking for them.Although not formally tested, JB's everyday memory is apparently normal for his age, with his exceptional memory for Milton's poem apparently arising from his relentless practice and dedication.
This is a common pattern in mental practice or 'brain training' style scenarios where we get better at the tasks we repeat but that improvement doesn't seem to carry over very effectively into other areas of mental life.