Sounds normal to me based on my experience. My DS lost his first one 1mth before his 7th birthday (had been wiggly for about 6mths). Then he quickly lost another 3. It took 9mths for the 1st one to even start to grow in (let alone drop down fully)! Then the others followed suit shortly after. He's been losing his other ones consistently since then. From what I understand, the later they lose them, the better it actually is for the jaw and for teeth to have more space. My DD is 6 and 5mths and no wobbly teeth yet, so it seems she'll follow suit (she's got her 1st adult molar come in, and that is actually the first sign of them about to lose their baby teeth from what I understand).