Being hit up for another donation 2 months later is very frustrating

I donated to Khan Academy 2 months ago.  Because of that donation, I got a request 5 days ago for another donation.  Why hit up recent donors rather than people who last donated 6 months to 10 years ago??
I already donate massively of my time by spending at least a dozen hours a week answering Questions and Help Requests.  I point out mistakes and problems (which mostly do not get corrected or solved) in an effort to make the website better for all learners.

Somebody make it make sense.