If I'm not carrying at least 20lbs. in my daypack, in goes the solar-powered, double-insulated, titanium coated espresso maker.
..the only way to go!
The others do have good points about the conditioning effects of the extra weight. We used to put in gallons of water for conditioning hikes in scouts (yeah, that was always fun, lugging around 35lbs of water for no reason).
..perhaps like many of you, when preparing for a particularly long or strenuous day hike i put a 25# plate in my backpack while on the treadmill, stair stepper or elliptical trainer - it raises a few eyebrows, but it's helped me be better prepared.
bsmith