Latex balloons deflate easily. To slow down the deflation process, you can tie a tight knot in the neck of the latex balloon. Attaching a ribbon can also help somehow. If you are attaching a ribbon, make sure you tie the ribbon below the knot.

You can also look for latex balloons that have been treated with Hi-Float before dispatch, or treat them with Hi-Float before you inflate them. Hi-Float is a non-toxic gel that goes inside a latex balloon as a protective layer to fill in the pores of the inner balloon surface so helium or air does not escape.