apple doesnt make the hard drives, the subcontract it out to other companies like samsung, toshiba, etc.
most feel as though it is not a question of if a hard drive will fail, but rather when. like a car, some last longer than others.
furthermore, the small size and dimensional constraints of laptop HDs make them more prone to higher failure rates.
as for if you should back up your data, it is completely your choice but IMHO i think people are crazy when they do not back up their data on a spare drive.
all of that being said, the time capsule does a lot more than simply back up data. you can get a wired portable HD for cheap, configure it with apple's time machine program, and achieve the same result. but if you like the additional features of the TC (automatic wireless backups, wireless printing) then its a useful item to have.
best of luck in RN school. i highly advise working as a tech/NA in an ICU during the summers to get additional experience. pays off big time after you graduate, and often gets your foot in the door as far as getting hired at the hospital you work at.