The pathogenesis of ectopic gastric mucosa is a matter of debate between a congenital-embryological-and an acquired origin-consecutive to a gastroesophageal reflux (GER) like Barrett's esophagus -, the most commonly accepted theory being that these areas are embryological remnants.
Standard size latex filled helium balloons stay afloat for approx 8 - 12 hours, metallic helium filled balloons float for 2-5 days. I have found that a 36 latex helium filled balloon can stay afloat for a number of days due to the thickness of the balloon and the massive quantity of helium.
A hot air balloon requires a great deal of fuel to keep it aloft, so that you can't fly it even for one day. A gas balloon, which usually uses helium, has the problem that the helium cools at night when the sun is not on it, and you have to throw ballast overboard to keep it from going to the surface.