Just to correct a couple of anomalies by G1991.
You cannot, and never have been able to bid for more or less night stops. You can request to be placed on minimum, normal or maximum night stops, but your preference is just that, a preference. This means nothing in the grand scheme of things. We've had pilots on maximum doing minimum and pilots on minimum doing maximum, all in the same base. I was on minimum night stops and still being rostered between between 10 & 15 nights away per month.
The second anomaly is that you will not be rostered a minimum of 3 days off after working 6, it is a maximum of 3 days off. If you get more than 3 then consider yourself very fortunate and in the minority.