Our local Fire and Rescue Service appliances are fitted with hoses which are much longer than 45m.
The 45m criterion is based on the physiological demands on firefighters engaged in search and rescue and on the restrictions that may be imposed by their equipment.
When considering hose length it is important to appreciate that, in practice, hoses have a tendency to "snake" when charged thus limiting their effective length. It is also common practice to trim the ends of hoses where they become damaged. The time and effort it takes to lay out a hose may also be an important factor.