The firm explains: "When you purchase a new mattress, there is always a settlement period to think about. Mattress settlement is a process during which the materials inside it compress and conform to the shape of a sleeper's body. It's also a normal part of adjusting to a new mattress. Just as you have to get used to your new mattress, it needs to get used to you.
"During the mattress settlement period, more frequent mattress flipping and rotating is necessary. This can vary from one mattress type to another so it's always wise to read through the mattress care guidelines issued by the manufacturer when you remove your mattress packaging.
"As a general rule, we'd recommend flipping and rotating (or simply rotating if you have purchased a one-sided mattress) it on a fortnightly basis. This helps to prevents hollows from forming in the sleeping area. And we also recommend flipping and/or rotating your mattress every two weeks for the first six months following its unboxing or unpackaging."
After the initial six months, you then need to flip or rotate it at different frequencies depending on what type of mattress it is.
A memory foam, latex, hybrid or orthopaedic mattress doesn't need to be flipped.
But a pocket sprung mattress does need to be flipped "every three months" at a minimum, confirms Benson for Beds. An open coil mattress must be flipped every month.