DS12 was one of what I think is about 50 6th graders in the US to qualify this year to take the AIME (did not do well on the AIME). He probably spends 10+ hours most weeks on math in addition to his Algebra II class he takes at school, so maybe around 15 hours in total per week.

He did much better on the AMC test than he did at MathCounts. AoPS is wonderful.