Okihara,
In answer to your question. Technically yes you can renew the ASIC well before expiry in fact a lot of people do. If you go through the same issuing body they would probably ask to get your current ASIC off you before issuing the new one. I don't want to start the debate about having two cards, yes I know a lot of people do and for very good reason. Although the legislation is a bit unclear in this regard, there is nothing stopping a person from doing so.
KingRB,
12 weeks is an absolute worse case scenario. Most issuing bodies are averaging about three weeks to get the clearances through and in many cases a lot less.