Zander's was when he was 9 days short of turning 6 months - he was born in March so when I though he was getting big enough it was too cold so we waited for the weather to start warming up again!

My younger brother & sister are 16 months apart, so mum was busy being pregnant & sick (LOL) to have my sister done straight away. She had them done together when my sister was 2 and my brother a few months old.

I don't think there really is a set time to do it though.