Is it worth seeking disability accommodations if I get good grades anyway?

I have bipolar disorder and take medications that make me foggy and confused. Because of this I am thinking of asking for extra time on tests. But I generally score in the upper half of my classes, even when I am taking my medication. Should I still register with the disability office?

Also, my advisor is teaching the class I'm taking, and many of the TAs are people I already know, who may think I am trying to game the system.