Sorry for the really delayed response, it's hard to keep up with comments at times.

Yeah - you are changing your keys on your account. It's "forever" until you decide to change it to something else.

can i create another account with eos voter?

Yes, it's under Tools -> Create Account. It requires an existing account to create (and pay for RAM) for the new account.

to have another public and private key, how can i do that?

Yep! Tools -> Key Generator will let you generate an unlimited number of new key pairs.