On some light a/c I've flown, I've seen up to 7 deg compass swing with pitot heat on/off. I believe compasses are swung with all services on, including pitot heat. Thus, even on a warm day VMC flight, I select pitot heat on to ensure compass is within card readings, THEN align DI with it as a part of the vital actions before t/o. This ensures minimum time on the ground with heat on, but aligned DI and compass within limits. Then, final cross-check of DI, compass and runway QDM once lined up and before rolling. This only takes a few seconds but all this drill was how I was taught it for the IMC rating years ago.
Standing by for more disagreement!!
The Odd One