Latex balloons filled with helium last between 12 to 48 hours, depending on the size of the balloons; if filled with Hi-Float they last about two to 14 days. Hi-Float is a liquid protective coating that is inserted into the balloon and spread around to prevent helium from escaping as quickly.
Float times for balloons vary depending on the conditions they are kept in, how they are handled and the size of the balloons. Balloons are adversely affected by heat, wind and sun, so it's best to keep them stored in a cool, dark place until they are needed. Latex balloons do not stay inflated for nearly as long at mylar balloons, because latex is a porous material.