Every once and a while I'll get one and then again, I may get 5 or 6 credits in a row but then they don't come any more unless I give reputation to people.
So, as a result, I concentrate on giving reputation rather than posting replies for which I get no recognition.
In turn, I have achieved 541,315,115 or a little over a half billion reputation points.
I went up to the local coffee shop armed with those half billion reputation points plus $1 and received a cup of coffee.
I can give reputation to a one post newbie and instantly fill his banner up with a full complement of all color A's and little rectangles jumbled together.