Just food for thought. People react differently to Deet as it relates to its ability to repel. So it is not a one size fits all. Typically, however repellent is needed for a short amount of time if for example you are fighting off mosquitoes.

With that in mind, 15% and 100% Deet will have similar performance for most people for 2 to 4 hours. Everyone has a different effectiveness time frame. The 100% Deet will keep going. But if you apply at 7pm and crawl in your tent at 10, it is highly likely the 15% product will perform as well as the 100%. If it wears off, apply again and it will be effective with still less exposure to Deet.

But it is critical with any strength, the application is complete especially on exposed skin. If your skin is not in contact with Deet it will not perform. This is not a perfume. So rubbing on for coverage is the best approach. Washing hands after is a good idea too not just for health but for the points made below.

A couple of personal thoughts. As pointed out in some of the earlier posts, Deet will affect plastics, paint and some fabrics. Do not let it come in contact with your bike, tent painted things etc, regardless of the % of Deet. And for cost savings and limiting chemical exposure you are better off using a lower deet product, executing a good coverage method such as wiping it on your skin. If you find yourself being a 'short runner' meaning it seemed to lose its effectiveness in under 2 hours, apply it again.