You will want to have a tune up much more often than once every five years, assuming that you practice daily, and ESPECIALLY if you are in a marching band.
While in high school (I just finished my first semester of college, so this is recent news), I got my sax tuned up after every big parade (we didn't do field shows, and maybe one parade a month or so). I realize that this is excessive, but normally a long bus ride will work "wonders" with your instrument.
After sitting in the compartments in a hot day, some of my keys would go out of adjustment because of the constant jolting combined with the heat semi-melting the shellac holding the pads in place.
My repair tech recommends, at least, a biannual tune up (every two years), with less time in between the tune ups if you play more than the average high school saxophonist.