It really depends how often you are going to use your hot tub. If you use your spa every day then it will cost you more to heat the water back up every day when you want to use it. If you are going away or don’t intend on using your hot tub for a longer period then it is advisable to turn the temperature down.
Some hot tubs have remote monitoring systems that allow you to monitor the health and temperature of your hot tub while you are away. Well designed hot tubs like ours are designed to be highly energy efficient. So much so that it costs more to reheat the water back up to temperature when you turn it down. If you have to wait for the water to heat back up again you may not use your hot tub as often.