If so, is there any preventative measures I can take to prevent candy from expiring?  I'm curious because Halloween candy after two years tends to look a little...off, and I'm not sure if it's safe to give it back out this Halloween.  Since there's no noticeable expiration date on candy packages, is it safe to assume that they don't expire?  Same goes for homemade candy, does it expire too?   I want to know for the majority of chocolate-based candies, rock-sugar candy (jolly ranchers, etc) whether or not they expire 
Hard candy (I think called boiled candy in England), such as lollipops or star mints is essentially pure sugar, with some color and flavor added.  This type of candy will last essentially forever, if kept absolutely dry.  There may be some degradation to the color or flavorings after six months or so, but the candy itself will last indefinitely.  If moisture can get to it--even summer humidity--it can soften, become sticky, clump together, and otherwise become unappetizing.  Chocolate has a fairly long shelf life, especially dark chocolate.  Under proper conditions, it can last for several years.  The mix ins or other components of a confection may limit its shelf life:   Nuts may go rancid after a year or two Nougat may dry out and get rock hard, or if it is humid, spoil Caramel may get very hard   One manufacturer suggests a shelf life of 6 months for its candy bars, which is probably a reasonable estimate for good quality.  See also:   What is the shelf life for chocolate chips? Kansas State University: When Sweet Treats go Bad  