Seven. One to change it and the other six to sing about how good the old one was.
or
Just one, provided there is a programmer around to explain how to do it.
or
Drinking, bathing, washing, swimming, etc.
or
The lettuce came in ahead, the egg got beat and the faucet is still running.
or
Neither, they all burn shorter.
or
They can make little things count.
or