I try to get my field points and broadhead hitting together, but if I can't I don't lose too much sleep over it. I spend a lot of time bare shaft tuning to get the arrow flight I'm looking for. If I get the bare shafts flying straight and I'm punching bullet holes through paper, and arrow flight looks good with the broadheads on, I don't worry too much about where my broadheads hit in relation to my fieldpoints. I've had them close, but never perfect. I wouldn't recommend that you wait until a week before the opener to practice with your broadheads though. Give yourself at least a month IMO, depending on how often you shoot. Better safe then sorry.

-Rob

edited to add:

By the way, this is my first year with the Slick Trick Broadheads. I bought them specifically for that reason. Theoretically, once I get my bow properly tuned and field points dialed in, I won't have to readjust my sights for the broadheads. Hope they work as well as everyone says!