Consider using scrolling BufferedImages instead of completely repainting graphs.

[InsertCreativityHere]

The current rendering strategy for graphs is to clear the graph display, and redraw it from scratch everytime with calls to drawLine(...)

It might be worth looking into instead rendering everything onto a BufferedImage and 'scrolling' it instead, so that instead of redrawing the graph everytime from scratch, we'd only have to paint 1 extra line to the BufferedIMage, then perhaps 'scroll' it before displaying, which may be more performant.