Rags,
I was on the generic duragesic patches (75mcg) for a few months at the beginning of this year (I switched back to oxycontin in the summer because the patches started giving me a heat rash).
I never tried the name brand patches, but I did try both generics (sandoz and mylan) and in terms of pain control the sandoz was much better for me.... and I also noticed that there was always gel left over when it was time to change to a new patch (I changed mine every 60 hours - every two and a half days).
One thing I did notice almost immediately after I started using the patches was that I got much better pain control if I used Tegaderm-type covers over the patches. (I used Invacare brand because it was much cheaper than actual tegaderm).
For me, the patches stuck well enough on their own but I got the covers just in case, and the first time I used a cover I noticed better pain relief. I tested the theory by trying the patches with and without the covers and overall my pain relief was much better when I had a tegaderm-type covering. I have no idea why the covers helped with better pain control, but it was working so I didn't really care why.
My point here is that maybe using a cover would help you too - it's at least worth a try.
Take care,
Liz