The term 'demand too much of' can be summarized by two crossword solutions: 'overtax' (7 letters) and 'overstrain' (10 letters). Overtaxing is the act of taxing someone or something beyond what is reasonable or necessary. Overstraining is the act of putting too much strain on someone or something, often leading to exhaustion or injury. Both of these terms refer to the idea of asking too much of someone or something, which can lead to negative consequences.