Misc: in greek mythology how many heads did hydra have?

Questions

"---------- expands according to our willingness to put up with it."- Barry Farber?

"---------- is a word used in advertising circles to refer to any incident to which the word "emergency" cannot be applied."- Fred Allen?

"----------- is one of the permanent and certain characteristics of a vigorous mind,"- Samuel Johnson - 1751?

"You can never plan the ----------- by the past."- Edmund Burke?

"You can observe a lot by ------------."- Yogi [Lawrence Peter] Berra?