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.
Why do helium balloons rise and fall? At one point in the afternoon they were dropping but later in the evening it was fully upright again. ... The weather did go from a little rainy and overcast to dry and slightly clearer skies later. Likely many droplets of water adhered to the helium balloons, when the weather was rainy, and made them heavier. When the water evaporated the balloons became lighter and rose again.