You can stay in a hot tub for up to an hour safely without any health issues.
However what I would recommend is to get into the hot tub and then sit in the hot tub for 30 minutes and then get out of the hot tub and allow your body to cool down.
Then get back into the hot tub after 15 to 20 minutes later and sit in the hot tub for another 30 minutes which would equal the hour in the hot tub.
Or if you want too you stay in the hot tub for the full hour and then get out of the hot tub and take a break from the hot tub for at least an hour.
Then get back into the hot tub again for another hour.
Staying in the hot tub longer than an hour can overheat your body and cause some health issues.
But using a hot tub in moderation can be good for your health as well as burning off calories for weight loss.