Every child I've had ver LOVES these, be it little 18 month olds to 7 year olds. They are the sturdiest magnetic toys on the market, which is important as the earth magnets are very string and can be fatal if they are swallowed.
My son knows to care for them, but I've had to take them away from some smaller children who wanted to throw or hammer on them, as it could risk fracturing the plastic and letting the magnet fall out. I count the pieces, and inspect them to be sure the plastic isn't cracking, but none have broken after more than a year. They have a handy box in which the pieces fit well, so it's a good way to make sure you've collected all the pieces.