How long are SAT scores valid?

My son is 15 years old and he will be taking the WAEC in Nigeria next year. I would like him to start preparing for the SAT as well, but I’m not sure when he should plan to take it. How long are SAT scores valid for admission to U.S. Universities?

We've already answered this question in another place on the forum. Please see our response about whether SAT scores expire here.