Hmm... I do wish lithium was discussed outside of the expert panel. Even though it's a small amount, certain common drugs do interact with it, such as ace inhibitors.
100% suggested rda is unlikely to be an issue. the most likely suggestion will be that the product be taken in 1/2 dose so that cuts it down ever farther. there are quite a few nutrients that interact with different medications, e & k and such, so it wouldnt have been wise to single out and not include any essential micronutrients based on their potential interactions with drugs.
How safe is 2-4x RDA for lithium? Seeing as I am on an ace inhibitor, I can't say I'm fond of the decision to include it. If someone felt 'dulled down' (as posted above) at 3-5 mg, you may wish to warn people taking ace inhibitors and other drugs about the interaction, as I think ace inhibitors can cause a 2-4x increase in lithium levels.
2-4x is perfectly safe, not counting any interactions with medication. average lithium intake is ~.5-~3g per day mostly from grains and vegetables. i can probably help you get a good estimate on your dietary lithium intake if youre interested. i'll take note of your advice, if you can PM me the name of your drug & any studies you have that would be helpful.