Well looks like you've already been given some good advice.
How long is a piece of string?
I find I get to the outskirts of the CBD itself, within 20-25 minutes, then it can take almost that long again to actually get where you need to go and park.
Given a good ride and easy traffic - 30 minutes all up.
Given traffic, roadworks and every other conceivable obstruction to getting where we want to go - an hour or more.
Buses, trains & trams are improving - good alternative if it works for you.
Peak Hour takes a full hour
Offpeak, 30 minutes to the city.
In peak hour it can take 30 - 45 minutes