Alot of it depends on what kind of student you are. Even if you have perfect SATs and a National Merit Scholar, I guarantee you wont be able to float by like you did in high school. As for myself, I'm not really a double major, but working on a major in electrical/computer engineering, a minor in chemistry, and a minor in mathematics, which is more than enough to keep me busy.
I could've graduated in 4 years with this courseload, but only if I did not have any extracurriculars or outside activities, which is NOT what you want to do, so its going to take me 5 years to graduate. By that time, I will have over 200 semester hours.
If you are really dedicated to working hard and strongly interested in both fields, then go for it. Don't do it just because you think it might look better, because it probably makes no difference at all in your admissions decision in the end.
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"There is nothing more powerful on this Earth as a man who has nothing to lose. It does not take ten such men to change the world--one will do." Elijah Mohammed