My friend's DF got their DS's done real early. I don't remember exacts but there was a lot of people going mental over it.

The professionals say that there has to be a certain amount of (I cant remember the name of it, but it's the part that gets peirced ) present before it is ok to do it.

IMO- As long as the professionals ok it and you are ready for it to happen then go for it. Everyone is different and so are their views.

I had mine done at four (I wanted them done and so did my Mother) but I just didn't wear earrings often so a few years later (quite a few) I had them redone because I couldn't fit studs in anymore, just sleepers. My sister had hers done at 10 and I have a lot of friends that get their kids done ASAP. They are just earrings and it has no impact on their quality of life so whenever you are ready, go for it.