My son is 3yr old, still sleep with me. I believe he will be ready to sleep alone around 5-6yr old. Although most mother believe "sleep alone" is good for baby, I personally think "too early" is not good. 我相信每個媽媽都有感覺, 有母親本能. 很多時候都會感覺到什麼時候做什麼事. 就好像動物一樣(當然我們和動物不是完全相同). 不過有時習慣被告訴而做成一種依賴他人意見. Anyways, this is my personal opinion.