I noticed that I have a little rep gain through old answers (not from old questions), maybe once or twice per month I get an upvote from stuff that is more that one month old.
If you suppose that every good answer has some probability of being discovered and upvoted by someone in a given time period, then follows that at a certain number of good answers you will get so many upvotes from old stuff that at one point you hit the rep cap every day.
So I suppose the answer to your question is: Yes, with a a certain amount of good answers you will eventually have this critical mass (I am still very far away from that point).
However, I don't think that it correlates to a spefic reputation threshold.
Some people just answer lots of questions and receive a few upvotes on most of their answers, others give fewer but great answers, and have a similar gain in reputation. But since they can only receive one upvote per person on their old answers, they get fewer votes from old answers (because they have answered fewer questions).
And then there are those who give lots of great answers. And one of them just posted his answer to this question...