TrueCrypt - Does the change of your passphrase have any effect?

Question

You can modify your password/passphrase in Truecrypt.
So it can be either 'foo' or some 64-char-long random password.

Does this have any effect on the encryption whatsoever?
Let's say you do a full-disk encryption with a long, good password.
Then you modify it to 'foo'.

And then you go back.
Did anything change except the password itself?
Do you always have to use a strong password? (Even if it's a temporary change.)

Reason: Fairly simple. Imagine you have a laptop with full-disk encryption. You are staying at home, you are on a vacation, whatever. Daily you use a very strong password to keep things protected, and to prevent brute-forcing. But typing that in all the time is a hassle, especially if you are in a safe place.
Thus, you want to modify/make the password easy/simple.

Answer 1

Changing the passphrase of a TrueCrypt volume only re-encrypts the volume's master key (randomly chosen during volume creation and stored in the volume header) with that new passphrase. TrueCrypt will not re-encrypt the whole volume. Just make sure, no one else has access to the volume header while the “weak” passphrase is in place.