Voltage regulation is another consideration along with mechanical stability. Before considering other possibilities of oscillator drift let's look at the causes listed here. As I said thermal considerations play a major part in oscillator drift. Consider just one example in close detail using nominal yet highly accurate figures, an oscillator designed for operation at precisely 7 Mhz. For this part we will assume neither the trimmer nor the inductor vary in value.
Re-read all that if necessary, it's a mouthful.
For our illustation we are saying the only influence on stability is our 82 pF fixed NPO capacitor when our temperature varies around 25 degrees. It's a capacitor where it's value theoretically should NOT change with varying temperature. Now the temperature after power turn on of our oscillator rises to 28 deg C inside our enclosure. It follows with a temperature rise of 3 degrees our capacitor is going to vary positive 3 X 100 ppm. That's almost a full kilohertz.