I'm still passionately interested in what my fellow humans are up to. For me, a day spent monitoring the passing parade is a day well-spent.
Taking on challenging projects is the way that one grows and extends one's range as a writer, one's technical command, so I consider the time well-spent.
A well-written life is almost as rare as a well-spent one.
As a well-spent day brings happy sleep, so a life well spent brings happy death.
Leonardo da Vinci
A comfortable old age is the reward of a well-spent youth. Instead of its bringing sad and melancholy prospects of decay, it would give us hopes of eternal youth in a better world.