When does it start to suck you ask.......with a loaded pack and you start up hill, down hill, side hill, over blow downs, under blow downs, over rocks ,through thick brush, through deep snow, through creeks, in the dark or in the sun. I am certainly not the most experienced but I have hiked enough in summer and packed enough elk out to know it's 2 different worlds. Packing weight on a trail or road where footing is easy and bending and climbing over or under logs isn't needed isn't a fair mile comparison. I pack what I can and never needed a scale to tell me it's too much or too little. Heavy, slow and sore or light, fast and tired? With a lighter pack for me it's just hiking not packing. I have packed out a shoulder and hind at the same time before and will never do that again. Now if I need to cut a hind in half to make it comfortable then so be it. I feel no need to have a fitness competition on the mountain.....I would certainly lose every one. For me it's all about hiking with whatever weight and being able to do it day after day after day or two a days for more realistic packing out of an elk. Maybe heavy pack in the morning and a lighter pack in the evening to simulate packing out of fronts and hinds.