When you buy candy estimate the amount you will use in a one month period. If it lasts more than 2 months I would buy less next time. If you find candy you don't know how long it has been kept. If you can't bend it don't eat it. If the wrapper sticks don't lick.
This depends on the type of candy, how long it was in the shop and the conditions under which it was and will be kept. Most types of candy will be kept for as long as 3 months, but only if they are kept in cool and dry conditions.
Yea it depends on the candy. Kit-Kats usually if they are not good they will turn really soft instead of crunchy and it will be kinda gross. But any gummy candy will probably stay good for a couple of months.