Are you serious? Even not eating for a week will not kill you and i would not call a link to a forum and a 5 minutes video, "sources". At the moment, other than the blog of one of the founders there is not much to read about this. What about some specialists taking a look at this before start selling it?
Rob wants to put this through proper clinical trials: http://www.youtube.com/watch?v=jTkuvppi334
As of now it hasn't existed for more than a few months so it's a little hard to give sources for trying it for "years".
Additionally, Rob strongly suggests NOT eating it every day.
As for problems arising months (or years), there's also a post about that too: http://robrhinehart.com/?p=570
A week long study? Scurvy takes months. Other deficiencies can take years. "We tried it on ourselves for a few months" is not evidence of anything.
Your original post's attitude seemed to imply it was almost risky to consume this as it's made by people aged "20 or so". Not only do I find your age discrimination shocking, I also take issue with your sarcastic tone.
If you want evidence, I can think of two sources:
[1] http://discourse.soylent.me/ -- Plenty of people on the discussion boards
[2] http://www.youtube.com/watch?v=I8WpksPED_Q -- Week long study