These are a great fit for my 5 1/2 month old who's very long and slim. She doesn't sleep through and will feed 3-5 times during the night, so she's a heavy wetter, but after washing these 5-6 times they're absolutely brilliant at keeping her dry for up to 8 hours. I have no doubt they would easily last from when she was put down until the morning if she slept through.
My baby is a tummy sleeper, so it's been tricky finding something that would sit high enough to keep her dry alongside her being very long. I've found folding the inner booster over twice and making it into a square helps keep her dry, then adding the fleece liner and an additional booster flat on the outside of the nappy before using the Little Lamb wrap works brilliantly. I will definitely be buying the next size up!