Doesn't Look a Day Over 99

Today is the 100th episode of Li'l Nyet, one of two webcomics I do with my wife. Our gift was a gratifying readership increase, which raised the question of how to best measure a "reader" vs. a "visitor." How many times over the course of a month does someone have to visit to be considered a reader?

I took an informal polls of colleagues and it was pretty split between once/week and twice/week. Of course, that's for comics that update frequently. I used Nyet for my example (five/week) but I think it would hold for three or four updates/week.

Of course, I wonder what methods people visiting this site consider to be best.