We have had companies that have died quicker because they had high burn rates, but we haven't yet let this consideration affect our investment choices.
Is there some self-selection going on where founders that think they can do more with less go for YC instead of someone else? Do people of the "first, let's buy aeron chairs, then we can worry about deciding what to make" mentality even know that YC exists?
I think the main reason we get more applicants in their 20s is that the older people are, the more difficulty they have getting n cofounders to be free of obligations all at the same time.