You don't have to animate the scale, as it is just that - a scale. Each large tick for example may represent 2 Seconds. So, you may have 2, 4, 6, 8 etc displayed on the X axis. In that example the sample will take 8 seconds to reach the right hand edge of the display. Then the sample starts again from 0.

One option would be to draw the first sample (0 to 8 seconds for example) then draw a new sample of back at 0 in a different colour. That way you would be continuing to display trend. Then on the third pass remove the first sample line (so two are always displayed) - for example.