Learn Hardcore Korean: sukbak gigan jung bangeul byeongyeonghage doemyeon yeyageul dasi hwaginhaeya haeyo. - If you end up changing rooms during your stay, you have to reconfirm your reservation.

중 means “during/in the middle of” and pairs well with nouns that denote an ongoing state (e.g., 근무 중, 통화 중).
동안 means “for/during (a span of time)” and highlights the duration.
In this sentence, both 숙박 기간 중 and 숙박 기간 동안 are natural. 중 sounds a bit more like “while in the midst of the stay,” while 동안 slightly emphasizes “for the whole period.”

Why is it 숙박 기간 중 rather than just 숙박 중? Are both okay?

Both work.

숙박 중 = “during the stay,” concise and common.
숙박 기간 중 = “during the lodging period,” a bit more formal and explicit (common in hotel notices).
You can also see 투숙 중 (hotel-specific) or 체류 중 (stay/residence).

What’s the difference among 숙박, 투숙, and 체류?

숙박: lodging/staying overnight; general-purpose word.
투숙: checking in and staying at a hotel; hotel register style.
체류: staying/sojourn (often in immigration/visa contexts).
In a hotel context, any of 숙박/투숙 is fine; 체류 is more formal/administrative.

Why is it 방을 and not 방은?

방을 marks the room as the direct object of 변경하다 (“to change”).
방은 would topicalize/contrast the room (“as for the room”), which isn’t needed here. The action is “change the room,” so the object marker 을 is the default.

What’s the nuance difference between 변경하다 and 바꾸다?

변경하다 is a Sino-Korean, more formal “to change/modify” (fits policy/rules, notices).
바꾸다 is native and more casual “to change/switch.”
In a hotel notice, 방을 변경하다 sounds appropriately formal. In casual speech, 방을 바꾸다 is fine.

Why use 변경하게 되면 instead of just 변경하면?

V-게 되다 indicates that something “comes to happen/ends up happening,” often due to external circumstances or as a softer, impersonal framing.
변경하게 되면 ≈ “if you end up changing (the room).”
변경하면 is a direct, neutral “if you change.”
Using -게 되면 sounds less direct and more courteous/impersonal—good for announcements.

Could we say 방이 변경되면 instead? What changes?

Yes.

방이 변경되면 uses the passive (“if the room gets changed”), focusing on the room being changed (perhaps by hotel policy/system).
방을 변경하게 되면 highlights the guest performing/initiating the change (softened by -게 되다).
Pick based on who/what you want to emphasize.

Who is the subject here? It isn’t stated.

Korean often omits obvious subjects. Here, it’s implicitly “you (the guest).” The ending -해야 해요 indicates a directive/obligation directed at the listener.

What does 다시 contribute in 예약을 다시 확인하다? Is 재확인하다 better?

다시 확인하다 = “check/confirm again,” plain and common.
재확인하다 = one-word Sino-Korean “reconfirm,” a bit more formal/official.
Hotels often use 재확인하다 in written notices, but 다시 확인하다 is perfectly fine and natural.

Is there a difference between 해야 해요 and 해야 돼요? And what about more formal options?

해야 해요 and 해야 돼요 both express “have to/must” in polite speech; 돼요 can feel a touch more colloquial/regional in some ears, but both are standard.
More formal: 해야 합니다.
With honorifics (addressing a guest): 확인하셔야 합니다 or 재확인하셔야 합니다.
Super-polite request style: …재확인해 주시기 바랍니다.

Is -면 here “if” or “when”?

It can be either, depending on context. In policy/instruction sentences, -면 often means “if/whenever” (i.e., in any case where this condition occurs). Here: “If/whenever you (end up) changing rooms during your stay…”

Can I drop some particles in casual speech?

Yes in everyday talk, particles often drop:

숙박 중 방 바꾸면 예약 다시 확인해야 돼요.
This is casual; in written announcements or formal speech, keep the particles as in the original.

Any pronunciation tips for this sentence?

숙박: often pronounced with tensification as [숙빡].
예약을: liaison makes it sound like [예야글].
되면: [되면].
Overall flow: 숙박기간중 방을 변경하게 되면 예약을 다시 확인해야 해요.
Spacing remains standard even though speech runs together.

What about spacing? Should it be 숙박기간 or 숙박 기간?

Standard spacing is 숙박 기간 (two words). You’ll sometimes see the closed form informally, but official rules prefer the spaced version here. Also keep 기간 중 spaced: 숙박 기간 중.

Can I move 숙박 기간 중 elsewhere in the sentence?

Yes, adverbial time phrases are mobile:

숙박 기간 중, 방을 변경하게 되면… (comma optional in writing)
방을 변경하게 되면 숙박 기간 중 예약을… (less natural since it can sound like it modifies “reservation” rather than the condition)
Best is near the clause it semantically modifies (the changing of the room).

How could I say this more politely to a guest?

숙박 기간 중 방을 변경하시게 되면 예약을 재확인하셔야 합니다.
Or as a soft request: 숙박 기간 중 방을 변경하시게 되면 예약을 재확인해 주시기 바랍니다.