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.
We recommend inflating latex balloons with helium as close to the event as possible in order for them to look their best throughout. As a rough guide, 10 inch balloons will float for around 8-10 hours whilst 12 inch balloons will float for around 12. However, factors such as temperature, who the balloon is manufactured by and what accessories are used will all have an impact.