When is 早く寝てろ used as opposed to 早く寝ろ?

Question

This question is about idiomatic usage of language. The grammatical side of the difference between 寝ろ and 寝てろ is clearly explained here. But I think there is another part of this question: in what situations should one be used over the other? I was recently corrected by a native speaker friend who said 早く寝てろ was incorrect. They said it should be 早く寝ろ. And it prompted me to think if I have been overusing 寝てろ.

Is the use of 早く寝てろ in the two examples shown below idiomatic? Why or why not?

Why does 早く寝てろ sound unnatural in some contexts? And in exactly what situations should we use 早く寝てろ no 早く寝ろ? More generally also: When do we say 寝てろ? When do we say 寝ろ?

Pic 1, source

Pic 2, source

Answer 1

「早く寝ろよ」は、「今から寝ろ」とか、「今日の夜に早い時間に寝ろ」という場合に使う感じですが、「早く寝てろよ」は、「早く寝て、とある時間には寝ている状態にあれ」と言っている感じがします。

例えば質問の2つ目の例でいうと、

「嘘だろ早く寝てろよ」は、自分が帰ってくる前に早く寝て、自分が帰ってきた時にはすでに寝ているように、という感じがします。

(1つ目の例は、文脈・状況がよくわかりません)

似た例を考えてみました。

「先に行け。/ 先に行って。」-- 今、自分より先に出発するように、ということに焦点を置いている感じです。
「先に行ってろ。/ 先に行ってて。」-- 自分は後から追いつくので、それより先に行って、自分が行った時にはそこにいるように、ということに焦点を置いている感じです。

Answer 2

I would feel "早く寝てろ" natural if the speaker's intention was to express "You should be in bed. You do need to have a rest. I am worried about you."

The phrase sounds very sympathetic. If you just want to say "Go to bed," "早く寝ろ" fits well in most cases.

It is somewhat broken because a straightforward translation would be like "Stay in bed soon," which might be the reason why your friend said it's wrong. This phrase may be the one the speaker cannot help but saying before thinking abount correctness.