Learn Hardcore Korean: daegi sigani gil ttaeneun hotel kapeeseo keopireul masimyeo gidaryeoyo. - When the wait time is long, I have coffee at the hotel café while waiting.

It topicalizes the whole time clause: 대기 시간이 길 때(는) = “as for times when the wait is long…”
This often implies contrast or a habitual rule, as in “when it’s long (as opposed to when it’s not).”
Without 는 (just 길 때), it’s a neutral time phrase: “when the wait is long.”
You can also see 때에는 (more formal/emphatic than 때는).

Could I say 길면 instead of 길 때는?

길면 = “if/when it’s long” (conditional). It’s fine here: 대기 시간이 길면 호텔 카페에서…
Nuance: -면 frames it as a condition each time; -ㄹ 때(는) frames it as a time-situation/habit. Both are natural; choose based on whether you want a conditional feel (-면) or a time/habit feel (-ㄹ 때).

Why is it 길 때 and not something like 기을 때? How is -ㄹ 때 formed?

Do I need both markers in 대기 시간이 길 때는? Is 대기 시간이 길 때 also OK?

Yes, 대기 시간이 길 때 is perfectly fine.
In 대기 시간이 길 때는, 이 marks “대기 시간” as the subject within the time clause, and 는 topicalizes the entire time clause. It’s common to “stack” markers this way.

Why use 대기 시간 instead of 기다리는 시간? Are both correct?

Both are correct:
- 대기 시간: set phrase, concise, slightly formal/technical (used in services, notices).
- 기다리는 시간: more descriptive/neutral.
You could also say 기다리는 시간이 길 때는… with similar meaning.

Is it written 대기시간 or 대기 시간?

You’ll see both in real life. The solid compound 대기시간 is widely accepted, and 대기 시간 (spaced) also appears often.
Pick one style and be consistent; you won’t be misunderstood either way.

Why is it 호텔 카페에서 and not 호텔 카페에?

에서 marks the place where an action happens (at/in the hotel cafe).
에 marks destination or location of existence.
Since you’re performing actions there (drinking, waiting), 에서 is the right choice.

Why not say 호텔의 카페?

Native usage usually forms compound nouns without 의: 호텔 카페 sounds natural and concise.
호텔의 카페 is grammatical but feels bookish/overly literal.
Alternatives: 호텔 내 카페, 호텔에 있는 카페.

Is the object particle 를 in 커피를 necessary? Can I drop it?

What’s the difference between -며 and -면서 in 마시며 vs 마시면서?

Both mean “while V-ing / as V-ing.”
-며: a bit more formal/literary, often used in written narrative or when listing simultaneous actions.
-면서: the most common in conversation; can also carry a “contradictory” nuance in other contexts (e.g., criticizing: 말은 그렇게 하면서…). Here, 마시면서 is the everyday choice.
So: 커피를 마시며 기다려요 (neutral/formal-ish) vs 커피 마시면서 기다려요 (very natural spoken style).

Could I use -고 instead (마시고 기다려요)?

Can I swap the order and say 기다리며 커피를 마셔요?

Grammatically yes, but the action before -며/-면서 is background; the final verb is the main action.
- 커피를 마시며 기다려요 ⇒ main action is “wait,” background is “drink.”
- 기다리며 커피를 마셔요 ⇒ main action is “drink coffee,” background is “wait.”
Choose the one that matches what you want to emphasize.

Why 기다려요 and not 기다립니다? What level is this?

기다려요 = polite “요”-style (해요체), friendly/polite in daily conversation.
기다립니다 = formal “합니다”-style, used in announcements, writing, or formal speech.
Either works; the sentence reads as a personal habit, so -요 style fits well.

Why is it 기다려요 (여) and not 기다리어요?

Contraction rule: -이 + -어요 → -여요.
기다리- + -어요 → 기다려요. Same with 가르치다 → 가르쳐요, 피우다 → 피워요 (note slightly different vowel behavior).

Could I say 기다리고 있어요 instead of 기다려요?

기다리고 있어요 = “am (in the process of) waiting.” It describes an ongoing action right now.
기다려요 in this sentence expresses a general/habitual action (“I (usually) wait…”).
Since the sentence states a habit, 기다려요 is better. Use 기다리고 있어요 when describing a current, ongoing situation.

Is saying “a long wait” with 길다 natural for time in Korean?

Yes. Describing duration as 길다/짧다 is idiomatic: 대기 시간이 길다/짧다.
Alternatives exist but change nuance:
- 대기 시간이 오래 걸려요 (it takes a long time).
- 오래 기다려요 (I wait for a long time).
Your sentence with 길다 is perfectly natural.