My experiment has ended so I'll report the results. In the end I left it under the LED lamp for a few hours short of eight straight days. The lens is for all intents and purposes clear. I compared it side-by-side with an SMC Takumar 55mm f1.8 lens, which should have no yellowing, by looking through them both outside in broad daylight on a nice sunny day, and they were identically clear. All up I'd say it's a great success.