DD was the same age as yours when she got her first tooth (sam thing, bottom 2 came up at around the same time - a few days apart i think)
her teeth all came through super quick, she had all her baby teeth (except obviously her 2yo molars) by her first birthday.

i dont think theres a "right" time, i know that because she got her teeth so early seeing a baby with no teeth looked funny (which isnt supposed to be an awful funny, but a very cute "omgosh, its all gummy smiles" funny)
by her 1st birthday i still had friends with babies the same age whose first couple were still coming through!

poor things, it shouldnt happen so early they dont know whats goiing on