Constant high temps is not the only concern. Temp swings are as well.
Intel non Z motherboards barely have any heatsinks, if any, and they do fine for years, if you are not introducing more voltage i dont think you should have much of an issue as long as you case has some airflow.
Their documentation does warn specifically about the need for an HSF.
Which doesn't mean heatsinks would help much of course, epsecially flashy heatsink which seem to have a marketing purpose. Asus in particular had a few flashy and sometimes expensive but ineffective heatsinks on low-power fanless boards.