Permithrin works wonders.
Did a 6 week trip this summer, starting on the Canadian border ~July 4th. The skeeters were *smeared*, not swatted, and before your hand hit your other wrist, they were already hitting your elbow again. And drilling STRAIGHT THROUGH the DEET.
In resolving some gear issues, I bought my kids some ExOfficio BUGOFF zip-off pants with the woven-in Permithrin.
Worked wonders. In the next 4 weeks, there was no rash (no undies, either), and not a single insect, on the kids pants. Hundreds of miles, a healthy amount of rain (some every day for 3/4s of the time), and a couple of laundry washings -- and skeeters/black files right to the last day.
$50.00 a pop for KIDS [!] zip-off pants. Money well spent.
Sloetoe