Some guys hike the mountains with a pack that weighs 80# for hunting and some guys ride a side x side to a tower blind....what type of hunting are you preparing for?
So far I haven't been doing heavy pack workouts, but I do hikes carrying my son on the weekends. That pack weighs around 40# and I have no problem doing 8-10 miles or more with him.
Don't overlook carrying extra pounds on your body. I used to think I was in pretty good shape, but then I started eating clean, lost over 15lbs and feel a heck of alot better.