How long is the shelf life/expiration date? I am planning to buy a lot and want to know if that would be an issue

I have this on good authority from the CEO of a large vitamin company. Expiration dates are forced on them by the FDA. Vitamins can last years past the expiration date. Prescription drugs never go bad. However improper storage of vitamins can ruin them in an afternoon. Try buying your vitamins and leaving them in the car for the afternoon (in summer) while you go shopping and I guarantee they will not work properly. If it's too hot for a living thing it's too hot for vitamins. Use common sense. if the vitamins or drugs look fine they are fine, if they look damaged avoid them. period Im currently taking these a year and a half past expiration. they have never been hotter then high 90s. They are working fine.

What does it work best on?

This supplement is best to relieve sinus pressure and allergies sypmtoms.

do you sell a-c carbide in larger size?

Standard Process A-C Carbamide comes in both a 270 and 90 count size.

Wheat grass in arginex

There is no wheat grass included in the ingredient listing. Standard Process always suggests you consult with your health care professional about any concerns with ingredients.