Since the trip is always heading west, I think the jet lag wouldn't be too bad. My bigger issue is that I think you could get better flights by just going business with a regular carrier than doing the private 757. From the pictures I saw, it really isn't glamorous.I recently traveled with someone that did one with another group. His trip was 21 days. Honestly, it sounded exhausting. It would be cool for a few days, but they were never anywhere very long, and I think by the end my jet lagged and constantly "what time IS it?" confused brain would be miserable.
After talking to him, I filed that type of trip under "never".