Расстойка длится два часа.

Расстойка is a noun used especially in baking. It refers to the proofing / rising stage of dough, when the dough is left to rest and expand before baking.

So in this sentence, расстойка is the thing that “lasts” two hours.

Длится is the 3rd person singular form of длиться.

• infinitive: длиться = to last
• расстойка is singular
• so the verb is also singular: длится = lasts

That is why the sentence literally works like:

• Расстойка = proofing
• длится = lasts
• два часа = two hours

So: Proofing lasts two hours.

The dictionary form is длиться, which includes -ся. In modern Russian, this verb is commonly used this way to mean to last.

So you should learn it as a whole verb:

• длиться = to last

Examples:

• Урок длится час. = The lesson lasts an hour.
• Фильм длится два часа. = The film lasts two hours.

After 2, 3, 4, Russian usually uses the genitive singular form of the noun.

So:

• 1 час
• 2 часа
• 3 часа
• 4 часа
• 5 часов

That is why the sentence has два часа.

This is one of the most important number patterns in Russian.

Because час is a masculine noun.

Russian has two forms for two:

• два for masculine and neuter nouns
• две for feminine nouns

Examples:

• два часа = two hours
• два окна = two windows
• две минуты = two minutes

Since час is masculine, you need два.

Here часа is in the genitive singular.

That happens because numbers 2, 3, 4 normally require the counted noun to appear in that form:

• два часа
• три часа
• четыре часа

So even though the whole phrase means two hours, the noun itself is in genitive singular.

Because with verbs like длиться (to last), Russian often expresses duration directly, without a preposition.

So Russian says:

• Фильм длится два часа.
• Урок длится сорок минут.
• Расстойка длится два часа.

English often uses for, but Russian does not need anything like for here.

You might hear идти used with events or processes in some contexts, but длиться is the most straightforward and neutral choice for to last.

So for a learner, Расстойка длится два часа is the best model.

Compare:

• Фильм длится два часа. = standard
• Процесс идет медленно. = the process is going slowly

For a fixed duration, длиться is the safer verb to use.

Yes. Russian word order is flexible.

The neutral order here is:

• Расстойка длится два часа.

But you could also change it for emphasis, for example:

• Два часа длится расстойка.

That sounds more marked and puts focus on two hours.
For most situations, the original sentence is the most natural.

The stress is:

• рассто́йка
• дли́тся
• два часа́

So the full sentence is:

рассто́йка дли́тся два часа́

That can help you avoid common stress mistakes.

Yes, but the given sentence is simple and natural.

Some other ways to talk about time are:

• Расстойка продолжается два часа. = Proofing continues / lasts for two hours.
• На расстойку уходит два часа. = Proofing takes two hours.
• Расстойка занимает два часа. = Proofing takes two hours.

But Расстойка длится два часа is a very clear and standard way to say it.

It can do either, depending on context.

Russian present tense often expresses:

• what is happening now, or
• a general fact / usual duration

So Расстойка длится два часа can mean:

• The proofing is lasting two hours in this situation, or more naturally in English,
• Proofing takes two hours as a general statement.

Very often, it sounds like a general fact or standard duration.