It depends on the baby.

When Ash was first born, a BBB with longies was enough, as he got a little older (about the 3 month mark) I needed to boost it with another booster. Now he has night nappies (sandman and mirabai and zada) which he usually wets a decent amount (wet to touch, not sopping wet). Sometimes I go back to the trusty boosted BBB but usually now I will use a pul cover incase.