How often should I rotate my tires?

[In The Ten Ring]

I rotate my Accord's tires every 6K miles (and used to do an "X" rotation every 12K but the Honda shop was admamant only front-to-back was necessary).

1). How often should I rotate my 1972's tires (Custom 10)?

2). Should I do a front-to-back only or an "X" every other rotation?

3). *I am expecting to have non-directional all seasons on her.