Follow the instructions for inflation of the hot tub as you should not trespass the recommended PSI measure. For hot seasons this is quite important because the air will expand with heat, specially when the tub is set under the sun. Most pumps that are included with the hot tub include a gauge so you can check those measures. When you inflate too much the tub, pressure will start to damage the connections of the tub with jet heads, tubes and other orifices, and this will lead to leaks, so don’t overboard.
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.