Instead of using real water jets, they use air jets that blow the air around in the tub. This causes the water to cool down a lot faster than it would if you were to use a hard side hot tub. To fix this problem as much as possible, make sure that the one you go with is not made with materials that lose heat as well. If you do this, you should get about 20-30 minutes of good heat in the tub.
The heater once turned on, heats up the water at a rate of 2 degrees per hour. You can set the temperature beforehand, leave it overnight or during the day while you’re at work, then come home and soak in your desired water temperature. As with other models, this Intex portable spa comes with an insulated cover to keep the water clean while not in use. The cover also helps to keep the heat in until the time you decide to soak.
Ikaria also just happens to be home to one of the first, and certainly one of the most famous hot tub collections in history, as the island was known for its hydrotherapy. Was it the residual heat from Icarus' burnt wings that kept the waters warm? Probably not, but the healing properties of hot water have been used this way around the world for millennia.
They don’t usually use real water jets, but instead use fans to “blow” the air around (also because of the 120 volt outlet), which causes them to cool down much faster than a regular hot tub. This cooling effect is only made worse by the fact that the materials they are made from lose heat much faster than the materials used on a regular hot tub. All in all, you aren’t likely to get more than 15 minutes to a half an hour of good heat out of an inflatable hot tub.