Hard to say not knowing your current fitness level and experience. For a casual hiker I think 30lb would be relatively easy, 40lb might not be that comfortable any longer, 50lb could get tough already. For an adult male in decent shape, 40% of bodyweight is about the maximum load that can be carried on a longer term basis IME. That's 58lb in your case - but unless you're a serious hiker already I'm pretty sure you would not like to carry a backpack that heavy over a 150 mile trail, especially in more difficult terrain.

All in all, I prefer to travel light. My pack is rarely over 30lb even on longer treks, plus about 5-10lb on my belt, webbing and pockets (large canteen, knife, FAK...).