infinite switch data

How long are kiln infinite switches on and off? Analyzing the switch on my L&L Econo-kiln I roughly determined the equations to be:

On: y = .127x2 - .536x + 7.4545 Off: y = -6.9469ln(x) + 24.39

The slope loses correlation when the switch is on high (always on, never off). Aside from that, the r2 is pretty close.