Even if your equipment is shooting dead on you NEED to condition your muscles to be able to hold steady. I am an automotive machinist, I lift v-8 engine blocks with my hands, diesel heads and flywheels, Stuff like that.
I am not bragging, I am just saying that I am pretty strong and when our 5-6feet of snow clears and I can get to my shooting area, it takes a couple of weeks to get my muscles conditioned to shooting again. I wouldn't dream of throwing an arrow at a deer with fear of flinching or not being able to hold steady because of not enough practice. Man I shoot all summer long, its easy to find time, fun to do, and the least we can do for the game we want to harvest. We owe it to the animals to be as merciful as possible, that means nothing less than perfect shots. To do this one must be in perfect condition and that means lots of practice.
If you start now and are not overbowing yourself you have a chance to condition yourself maybe by the rut, but not by opener.
This is just my opoinion but alot of hunters will agree with me. Please take the time to practice, its fun, challanging, and the right thing to do!!!