or..
You could manually add the code below on your functions.php to extend your cookie expiry to whatever timeframe you like. You can, in essence, stop WordPress from ever logging you out by changing the number of seconds to be a much higher number.
add_filter( 'auth_cookie_expiration', 'keep_me_logged_in_for_1_year' );
function keep_me_logged_in_for_1_year( $expirein ) {
return 31556926; // 1 year in seconds
}