Will, a situation that is always expected to happen?

Question

I do think that in the long run, a vacation will make you more productive because you come back feeling more motivated and ready to work harder.

In this sentence, I think will is more likely to refer to a situation that is expected to always happen, not a situation that will happen in the particular future. So if I were using future preposition like 'next week', 'next year', it would not be appropriate. Or it would be better if I rewrote 'will always'.

And there are similar sentences.

More often than not, one family will have 2 or 3 cars.

There is always a friendly face greeting me and someone will always be on hand to hole the door open when I leave.

I'm always cautious to conclude something without your helps. So, I'd like to ask if I'm right to think this way.

Answer 1

... a vacation will make you more productive because you come back feeling more motivated and ready to work harder.

You are correct in believing that the 'default' interpretation of this sentence is what some grammarians call generic or habitual: it expresses a general truth about the consequences of taking a vacation, not a prediction about a specific instance.

In this case will does not express future reference but tendency; it is the same generic/habitual will you have probably encountered in the past tense:

When we were children we would go swimming every day.

This interpretation is pinned down by the use of the simple present come in the subordinate clause. In fact, you could use simple present in the head clause, too, without changing the meaning:

... a vacation makes you more productive because you come back ...

Consequently there is no need to add always to reinforce this reading. (In fact, always may be more than you really want to say—it implies that people never come back from vacation exhausted from their activity and resentful of having to return to the daily grind!)

However, it is possible to use the same main clause, with will, to speak of a specific future instance; but that will require you to change the form of come. It is easy to imagine a context; suppose your boss is talking to you:

Jihoon, I insist you take a vacation next week. I know you're very busy now, and you're unwilling to let the work pile up. But you're tense and grumpy; you're making a lot of mistakes; and you're actually creating more work than you're performing. And I do think that in the long run, a vacation will make you more productive because you will come back feeling more motivated and ready to work harder.

Answer 2

Your feeling about the first sentence is partially correct, but only because of the introductory phrase "In the long run". Using this phrase establishes that the near-term effects ("in the short run") may vary, but the long-term effects are more consistent. In this respect, you would be correct about the indefinite quality of "the long rung". However, adding a phrase such as "next week" could quantify just exactly what "the long run" means. "In the long run, stock values consistently rise, but this is not true over any period of a week or month", "In the long run, a week or more, you will see the conditions improve", "Things will get better in the long run, by next year at the earliest".

As to the larger question of the definite measure of "will", that is entirely a matter of how you use it. Generally, "will" is used to predict, since it describes the future, and predictions can be vague or specific. "Your package will arrive at 11:45 AM on Tuesday" is perfectly correct, and quite specific. Likewise, "A standard box of widgets will contain 144 units - no more, no less." (Although here "will" can be used as an imperative, equivalent to "must". It depends on context.)