Personally, I would wait until the piercing was completely healed without question before changing jewelry to help ensure the least trauma to the piercing as possible especially if you think you will change at a later date.  Changing the jewelry before the fistula has had a chance to heal can cause scar tissue that can make for issues down the road.  The only time you should consider changing before it's healed, is if the jewelry is giving you problems, and at that point, you should see your piercer to see what the best course of action is.

 Since I have the same question there's no point in posting a new thread.  When can I change jewelry in my conch?  It's a week old and the piercer said in 6 weeks I can change it.  Doesn't that sound too soon?  When will I know if it's fully healed?

 It will depend on your ear. I got my conch pierced a year ago and it's still not fully healed.  You, however, might be different. My answer to your question is fundamentally the same as my answer to the OP, unless the jewelry you have in is giving you fits, leave it alone until that hole is significantly healed.

 Cartilage can take 6-12+ months to heal...