Expired-date vitamins and supplements

I usually use my vitamins and supplements long before the 'use by' date, but I found a out-dated bottle of bulk Good And Natural vitamin C (Ascorbic Acid) 5000 mg.per tsp. and wondered if it was any good?

Hv, Is ascorbic acid a good form of vitamin C? I agree it's best to get vit. C from food or herbs.

Does it depend on the product if it is stable after the 'use by ' date?

Could you give us guidelines for out-dated vitamins and supplements? How long is OK?

Charly