How many magazines is enough is a commonly discussed topic. Presuming a person isn't collecting magazines to use for sale or barter, here is my answer. In the short term, I would have as many magazines as needed for a normal "load out" for each weapon, and about 25% of that many in reserve in case of loss, breakdown, or when magazines begin to malfunction. That way, there are enough magazines to rotate use, and replace magazines as needed.
For long term (as in magazines will never again become available) I would think at least twice the amount in paragraph one, but really, the sky is the limit. It is akin to asking how much ammo, how many bandages, how much food and water, etc. The basic answer is as much/many as possible.
