I read this on the packet too, and then didn't buy them. Our bedrooms get down to 5* and less in Winter. Keeping bedrooms at continuous 16-20* is crazy. How did we all survive growing up?
Really?! That's damn cold!! Lol!

The advice is based on the fact that babies (well kids and adults too) sleep best in a room that's 16-20 degrees. When we've holidayed and the rooms are colder (I think 12 degrees is the coldest we've experienced with the kids), I used the 3.5 tog bag, put extra layers on the baby and socks or mittens on their hands and socks over the wondersuit if necessary. I often put a spencer on under a Bonds Wondersuit in winter. Our bedrooms never get that cold though but we live in Perth. I tend to run a heater in winter if the nursery is too cool though.