Thanks to Al Lyman and Tony McCray for these tips!
If you're doing an iron distance triathlon and are making a multi-hour bottle of SE or Perpetuem for use during the second half of the bike course, the challenge you face for a hot-weather race is how to keep that second bottle cold. An ideal way to do achieve this is to wrap the bottle in a damp/wet face cloth or dish towel, and then freeze it the night before the race. The damp/wet towel literally sticks to the bottle and creates an additional layer, helping it to stay frozen longer. If it's possible to keep that second bottle of concentrated SE or Perpetuem on ice and in a cooler that will extend the "shelf life" and palatability factor significantly. If having a cooler at Special Needs is not possible, wrapping packs of Blue Ice around a bottle to keep it cold while sitting in a transition area is an excellent alternative.