<p>Something like a third of Oberlin students double- and triple-major - in fact, [url=<a href="http://blogs.oberlin.edu/about/ethos/double_or_tripl.shtml]here’s[/url">http://blogs.oberlin.edu/about/ethos/double_or_tripl.shtml]here’s[/url</a>] an intriguing blog post exploring why it’s so common at Oberlin (and what the point is of having a major anyway!) Most of the time it’s not at all difficult, especially if you decide early and plan carefully. But if you have two subjects that don’t overlap at all and you decide late to double-major, or you’re interested in honors or grad school (which may require extra prep), there is a chance it’ll take more than four years.</p>
<p>To give an example, I was considering a double-major in chemistry and Greek (with the goal of grad school in classics) and discovered that it would be hard to fit into four years and still take a healthy dose of courses outside either major. (That’s a problem I’d probably have at any college, unless it had extremely lax requirements for chem majors…) On the other hand, I discovered I could triple-major in Greek, Latin, and Archaeology, with a minor in chem - and no struggle to finish all three programs, meet my distribution requirements, prepare for grad school, take some random classes for fun, and graduate in four years feeling as though I’d learned what I wanted to learn 
But some people in similar situations decide to stick with both majors and stay longer. If you’ve got the time and the money for an extra semester, and you’re passionate about both subjects to the point where only a major will do, why not?</p>
<p>I hope that rambling made sense, and actually helped with your question…</p>