Why dose it prompt me to change my password and choose a certain time peroid to do it in?

Question

choose an option: daily, weekly, every 2 weeks etc.

Answer 1

What website are you talking about? Usually sites prompt you to change for security reasons, so your password can't be stolen.

IF it's my yahoo...I've never seen that option. Can't you just choose never?

Answer 2

The program is allowing you to tell it how secure you want it to be.  The more frequently you change your password, the better from a security standpoint.