Huh, is this bad? I typically cook enough rice in a rice cooker for two days and leave it out and haven't had any adverse symptoms...
http://www.nhs.uk/chq/Pages/Can-reheating-rice-cause-food-po...
> You can get food poisoning from eating reheated rice. However, it's not the reheating that causes the problem but the way the rice has been stored before it was reheated.
> Uncooked rice can contain spores of Bacillus cereus, a bacterium that can cause food poisoning. When the rice is cooked, the spores can survive.
> If the rice is left standing at room temperature, the spores can grow into bacteria. These bacteria will multiply and may produce toxins (poisons) that cause vomiting or diarrhoea.
> The longer cooked rice is left at room temperature, the more likely it is that the bacteria or toxins could make the rice unsafe to eat.
Reheating the rice does kill the bacteria, but does nothing to the toxins.
You might also consider the ambient temp of your kitchen. Pro kitchens run several hours a day, staying fairly warm the whole time (might have several ovens, tens of burners, and other hot equipment running throughout the day). Your kitchen, even with the rice cooker going, might stay fairly cool, and so bad bacteria has less time to grow.
Food safety is also talked about in terms of risk to different groups. Young children, pregnant mothers, and old adults are at higher risk than younger adults.