On my last trip I had 1000 dollars in hard cash in my wallet. Just a bunch of 20 dollar bills. I will also be doing the TA this summer and again I will start out with 1000 dollars. That should last for 50 days (= the entire trip) excl unexpected mechanical failures. Although I will carry 2 credit cards (emergency) I don't like using them at all because I "loose the grip" of where the money is going. But this behavior is probably reflecting the use of credit/debit cards in my everyday life: I probably use those cards 2-3 times a month. I need to physically see where the money is going. It is as simple and basic as it gets.
And remember the saying: