should a heat mat stay constantly at what its set to? like i've had mine at 28 and its been at 24-27 so i keep having to turn it up/down every few days, is this normal?
for an on/off stat there is a temperature that you set that the stat will turn off at and then once it has cooled by a couple/few degrees it will switch back on to bring the temps back up. Depending on the brand of stat you use you may get more of a variation then some others.
I have a habistat and a microclimate mat stats and the habistat has less variation than the microclimate. It usually holds temps within 1.5 deg. I have just bought a habistat pulse stat and that holds the temps within 0.2 of a degree. I will not be buying an on/off stat again.