All AVA high-pressure washers can be used with long extension hoses. You will have a negligable pressure loss when you and the machine are at the same height, and a marginal loss if there is a significant difference in height between the area you are washing and the machine.
AVA GO, EASY and SMART with their 3-piston pumps can easily handle a full 40 meters of extension hose without any significant loss of pressure. If the machine is 10 meters below the place you are washing, it is best not to have a longer hose than 20-30 metres. A greater difference in height creates an increased risk of overheating causing the machine will then switch off after a period of use. If this happens, you should consider moving the machine higher up/closer to the place being washed.
On AVA Master and Evolution, with their 4 or 6 piston pumps, you can have 100 meters of hose without damaging the pump if there is no difference in height. If the machine is 10 meters below the place you wash, it is best not to have a longer hose than 40-50 metres.
Master and Evolution can also be used with a greater difference in height than 10 metres, but the hose should then be as short as possible to reduce the potential for a drop in pressure or overheating.
As long as the machine is working normally, there is no risk associated with this, but if you notice that the machine switches off and on after some time, this indicates that the machine is overheating and the height difference is too great. This will vary depending on the charactoristics of the electric circuit that the washer is plugged in to.