do you think guitar players have something like a (life cycle) ? and which guitarist do you think reached a new unbeatable level in his performance ?

I think that's directly related to one's health and dedication to music. Andres Segovia played a jaw dropping solo guitar concert at the White House while in his 80's (maybe 90's??). There is truly no limit to a musician's potential. Recahing that potential is a whole other story.