See configuration menu 3 on the link below
http://customer.honeywell.com/techlit/pdf/69-0000s/69-2060EFS.pdf
Heating cycles
per hour
• 1: 60 min (steam, gravity)
• 3: 20 min (hot water, 90%+
high-efficiency furnace)
• 5: 12 min (gas or oil)
• 9: 6.7 min (electric
Make sure it is still set to 5 for 5 12 minure cycles per hour.
One other thing you mentioned in on of your posts.
(((Its pretty much always done this, I decided to change the thermostat b/c it was old and falling off its mounting. I assume all the regesters are open? is there a certain place i should make sure if the regesters are all open? air does flow into all the rooms, its just a question of shutting off before the target temp is met? is there a heat anticipator setting even on digital/programmable thermostats? I don't recall seeing anything in the instructions. Do you think that maybe its restricted ductwork? any way to fix that?)))
You said it has pretty much done this. So this problem was there before the new thermostat?
There has to be a reason the furnace is turning off before it meets the temperature requirements you set on the thermostat.
The thermostat controls the call for heat but other items like a defective high limit control, or other controls in the furnace can cause this to happen. I believe your furnace needs to be looked at by a professional especially since this has been doing this for sometime. With out specific meter readings and being able to be there to test it is all guess work here.