If you flow forward in the day of travel there should not be any charges.
If the flight is in March I would not worry about changing it at the moment unless they do it for free. There is every chance QF will change schedules between now and March, you will get advised that a change has been made. If this occurs do not accept it, even if it is only by 5 minutes call and QF and request the changes you are after. There will be no charge as it is an involuntary change.
If the schedule does not change and you are still not comfortable you can call up closer to the date and make the changes, they will still most likely charge the change fees.