Ballooning Technique What Kind Of Gas Or Inflation Technique Offers The Longest Buoyancy For A Balloon?

What kind of gas or inflation technique offers the longest buoyancy for a balloon? - ballooning technique

I throw a party of Nice, and a globe display is something that is desired by others to help you. However, I do not want to return the ball before then install all of them died on the floor when the guests arrive.

Also what kind of gas or inflation technique should be used to keep the balloons floating in the longest time?