My DS who is 8 years old has a few 'pet' subjects which are his absolute passions. He can literally talk or think or read about a subject from dawn to dusk without hardly any breaks. When I try to distract him by taking away any books he is reading and suggesting an hours break he gets very distressed. The only way of stopping him is to take him out for a walk or to his friends for a play. Is there any harm in just letting him absorb himself in that days chosen subject?