When your baby starts to sleep longer at night, you need a super-absorbent nappy. If they wake for a feed (or many feeds) but they're only wet so you don't want to have to change their nappy (and risk waking them up completely), the nappy needs to be really reliable. This is especially true for older babies who pee larger volumes and still pee a lot at night. The best type of nappy for wearing at night is a two-part nappy with a separate wrap. (These are also called fitted nappies, shaped nappies and night nappies.) The reason for this is that the nappy goes right round the baby, not just between the legs, so there is more absorbent fabric and it covers all of the bottom area. If baby decides to sleep on their side, or sat up in the the corner of the cot, the nappy will still catch the wetness. These nappies will also be useful whenever you need a nappy that will last a good long time without leaking - on a long car journey, for example, or going on holiday by air.
You will need to have 5-6 of your night-time nappies to allow time for washing and drying: one on the baby, one clean spare in the drawer, yesterday's nappy in the bucket waiting to be washed, and one or two washed nappies hanging up still drying.