My 5.5-year-old has just started getting them in the last year. He just has a very light sprinkling across his nose right now.
I started getting them when I was around 4.5 or 5, too, and had a face full by the time I was 8 or 9. I am still freckle-faced at age 24, although they are much lighter than they used to be.
Neither my DS nor I are redheads, either. I have very dark brown hair, and DS is blonde. Our freckles are small and light brown.