I'm just done with three years at Boston University in Computer Engineering... and I'm just shy of being done next semester (two courses short, I think).
And that's with taking more courses than I'm required for graduation (I liked the elective list I had), and taking only 3 courses rather than 4 one semester, and only taking more than four one semester, wait, two.
Most people I know are graduating in 4. There are some exceptions -- my roommate isn't going to be graduating in the next two years, and he's been in college for 5 years, but he should really drop engineering and learn to clean up after himself; the lab admin just walked this May, but has two courses left after four years.
So 4 years is possible, no problems. My girlfriend is getting a Biomedical Engineering Degree and a Linguistics degree in 4 years.