I haven't read through the entire thread...
Based on my very recent personal experience of this, I recommend waiting until your DD is around 12-13.
I think pierced ears are cute, but there is a lot of work required to keep infection at bay. At 13, your DD will be able to do the necessary cleaning herself.
My story:
DD1 (9) wanted hers pierced for her First Communion. Most girls in her class got them done recently. So we got DD1s ears pierced in the beginning of March. When I learned of the cleaning routine, I decided to do DD2 (7) at same time, planned to clean both sets of ears at same time, rather than face into this routine again in 2 years time.
We got them done at Claires, who provide clear details of the required cleaning routine along with cleaning solution.
First 2 weeks, I cleaned twice daily. Then I slackened off a bit, may once every two days, and by week 5 ears seemed fine, I stopped cleaning. (My bad, I know.)
Then around week 8, girls wanted 'new' earings. First of all, the back of the surgical steel earings were very difficult to remove, causing a bit of drama. DD2's ears bled a little, and the holes didn't seem to be properly 'healed' so I didn't allow her change to her new sterling silver earings, and put back in the original earings again. And went back on the cleaning routine for about 2 weeks. Ears then seemed fine again, but this time it was even harder to remove the backs from the surgical steel earings. So I gave up (at DD2 insistence!), and she still has these in (but her ears seem fine, but now she is too nervous to have them removed after ordeal last 2 times).
DD1s ears seemed fine, so we changed to sterling silver earings. Changed to new silver/pearl earings a few weeks later for the Communion. Went to change these again this evening (after about 2 weeks) , only to find her ears infected (pus in the holes when I pulled through the earings). I did thorough clearing, and put back in the surgical steel earings, but with stering silver backs, so I can remove more easily for a more thorough daily cleaning for the next 2 weeks or so.
I never expected ear piercing to be such a pain in the ass.
Very long - sorry.