at length vs by and by

at length

prep

  • For a long time. 

  • At last, finally, eventually. 

by and by

noun

  • Heaven; the hereafter. Usually preceded with "the sweet." 

adv

  • After a short time. 

  • After an indefinite period. 

How often have the words at length and by and by occurred in a corpus of books? (source: Google Ngram Viewer )