After reading this thread, there's only one thing coming into my mind, ''Am i a superhuman or what?''
I am not a super experienced cyclist, i carry over 40lbs of stuff + the weight of my bike and i never had difficulty going uphill.
Of course i am aware that with half the weight it will go faster and easier i guess, but, seriously, i don't care.
I like and use everything i bring, i also often carry for a week of food, i often ride country roads with not many town and even less many groceries.

I did many long hills and never heard myself complain about my load.
I will never cut weight in unnecessary things(thiings that i could survive without) such as my joggling balls, 3-4 books, drawing pad+ pens or my pair of hiking boots, just for the sake of riding faster and farther.