Here in Australia you can only keep them rear facing until they reach the carseat's weight limit...for most seats that is either 9 or 12kg...then you have to turn them around.
Unfortunately you can't buy seats here that have a higher rear facing weight limit...hopefully as more people realise how much safer it is they will start to produce hight limit seats.
I was trying to explain this to MIL the other day... Pie is still rear-facing at 20 mths & 11kgs, a shopkeeper spotted her like that the other day & said to MIL that legislation has been passed making it illegal to turn them before they are 2. I said to MIL that although that might be preferable I thought it was unlikely seeing as we can't get seats to suit over 12kg here
Will be interesting to see if it is brought in though.

A YouTube search brings up heaps of stuff on rear facing and why it's better.