My labor was 26 hours and we still managed to keep the birthing pool warm, mainly through keeping the 'lid'/cover on whilst not in it, and with some top ups with pans and kettles of hot water. I am v.tall so went for the regular sized birth pool in a box, it has the added advantage of a seat and great handles, it is deep and long. It was amazing and i could not imagine birthing anywhere else. Prior to buying this i did loads of research and thought i'd need a large (expensive) wooden heated one, but in the end it really was not necessary.