My children are 6, 7 & 8 and they all still believe in Santa. I think the world is a harsh place so why not let them have some fun in believing in things like Santa and the Easter Bunny while they are still young, it doesn't hurt anyone.
I personally won't burst my children's bubble until they figure it out themselves and ask me.
My daughter is very smart, so that probably won't be much longer, but until then why ruin it.
I remember the year i figured out Santa wasnt real because i noticed his writing was the same neat handwriting as my step mothers, so i asked her. I felt like i had lost something big when she told me he wasn't real. Something so fun, and that children get so excited for.