This post comes with a wildly inaccurate claim: I do not consider Crystal Skull to be part of the Indiana Jones canon. No fridge nuking for me.
There is a problem with these movies. Clearly, for the vast majority of the screen time, it is aimed at boys with swashbuckling ambitions. But for some fleeting (face melting) moments, it is too much George Romero, too little George Lucas. The films' climax scenes all seem to lend themselves to horror. Don't get me wrong, horror has it's place. It's just not appropriate for a 10 year old. But, all of the other scenes in these films are perfect for a 10 year old. The other problem is the same one I have for the Star Wars films; how do you keep these films for the right age when our culture is saturated with them? Some kid at my son's school is going to give away all of the good bits. And my son (with his film loving father) is going to miss out.
I'm going to go with 10 years on this one. This sucks.