I realize that all the cool kids play with their straps so long that the bass hangs down to their knees, but one of the first things I do with my new students is get them to adjust the strap so that the bass is in the same position sitting or standing, which generally means the bottom of the bass should be around belt high. I used to wear mine even higher, but for comfort's sake moved it down.
Wearing your bass too low causes several problems, some regarding playing technique, and some regarding long-term physical health. Let's start with the physical health, which may not be much of a concern for you at 18, but when you're 35, 40, 50 years old you'll wish you'd listened. Most basses weigh between 7.5 - 11 lbs, and some are even heavier. Strapping that sort of weight around your neck for 3-4 hours a night can cause back pain anyway, but by wearing it too low, you cause even more strain on your lower back. You could potentially develop disc problems and may even have to give up bass playing all together. It's worth it to wear it higher. Because wearing your bass that low puts the wrist of your fretting hand at an extreme angle, cutting off blood flow to the nerves in your hand, this playing position can also lead to severe carpal tunnel syndrome, which again may lead to you not being physically able to play bass anymore.
Furthermore, wearing a bass that low puts your hand in an awkward position and does not allow you to correctly fret notes with the pads of your finger tips. It prevents you from cleanly executing bass lines and causes all sorts of sloppy playing technique. You will likely notice less fret noise, and the ability to make cleaner transitions between notes and neck positions simply by shortening your strap length and moving the bass into the correct position. You may not look as cool, but in the long run, it really is about the music and I'd rather look boring and play killer music than look like all the cool kids and suck.