Homebrew PCBs

I've been thinking about the inactivity approach which can permit a 
tighter time control on the heaters = power savings & safety enhancement.
Some testing showed that when running a cool PCB thru the laminator the 
sensor temperature dips by a few degrees before the temp. control 
recovers as the PCB comes up to temp.
The current iteration of the mod, does monitor the temp sensor from a 
good/bad POV based on its outputs.

I can reflash my mod. PIC to track this and do the following:
1) Once the temperature has achieved steady state, issue  a single chirp 
every 30 seconds or so to alert the user.
2) If the steady state is unchanged for more than 15 minutes it 
indicates no activity and enables the heater shutdown/cooldown
3) If the temperature exceeds the max. setpoint of the laminator....also 
execute a heater shutdown.