I can not confirm this, because I haven't actually done it! But I have read "very credible posters" who claim to have had noticible improvements in resin production with only about 20-30 minutes of UV-b light exposure per light cycle. Others have run the UV-b lights for the full 12 hour cycle and get, roughly, the same results.
Now, this being said, this additional resin doesn't neccessarily make the bud more potant! Appearantly the "extra frosting" is just some sort of "Sunscreen Resin" that doesn't boost the THC content that much. I have never come across any "Scientific" explaination for this, so I take it all with a grain of salt!