# Future perfect with 'for'

To talk about an action that is still ongoing at a point in the future, we use the future perfect progressive with 'for' to emphasize the duration of the action:

By the end of September, I will have been working for the company for ten years.

In this case, the meaning of the sentence sounds similiar to one with the future perfect tense:

By the end of September, I will have worked for the company for ten years.

But what about these two sentences?

By ten o'clock, I will have been painting the house for three hours.
By ten o'clock, I will have painted the house for three hours.

I know the first sentence emphasizes the duration, as it is continuous. It's not about the completion of the action (painting).
But what does the second sentence emphasize?
Is the action (painting) completed here? Is it only about the amount of time that will have been spent on painting by ten?

I also know that the future perfect is usually used to talk about the completion of an action at a certain point of time in the future. But without 'for'

I will have painted the house by ten.

Meaning, if you come visit me at ten, the house will be painted. What about the same sentence with 'for+an amount of time'?

This is the question in a book

By the end of the day, we ....... the house for a week.
a. will have painted
b. will painted
c. have painted
d. will have been painting

• Your ssumption that if one form emphasises one feature of the situation, then a different form must emphasise another feature, is wrong. You're talking about the concept of markedness. The converse of marked (in this case, the progressive form emphasising the extended nature of the activity) is unmarked, where nothing in particular is emphasised. Commented Jun 24, 2020 at 19:20

By ten o'clock, I will have painted the house for three hours

You're communicating a checkpoint. Here, you are likely implying that at ten, you'll be ready to stop, you'll be ready to have someone else take over, or you will have reached/surpassed a goal identified earlier.

By ten o'clock, I will have been painting the house for three hours.

No checkpoint. You're communicating the duration of your painting at the future time of ten o'clock, and you either won't be done with it or painting the house is an action that has no definite end.

I will have painted the house by ten.

This, without additional qualifying words, means you will be done painting the house at ten.

I will have painted the house for six hours by ten.

At ten, Either you won't be done painting the house or painting the house is an action that has no definite end.

Housepainting is generally an action that can be completed, so expressing that painting the house is an action that "has no definite end" is not usual.

For a verb like soaking, where you can soak an item for some time but might leave it in there longer, and may not know exactly when you want to stop, that sense is more likely to be possible.

• Can you tell us, what's been written in front of this sentence? In some dialects of English, this is quite possible. In the literary English, this is a gross mistake. It should be something like this: The next day, we will have been in the state of painting the house for a week. Isn’t it easier to say, The next day, we will have been painting the house for a week? Commented Jun 24, 2020 at 17:12