Tren Hotel Lisbon to Madrid

I don't recall specifically for this run but generally you can board at least 30 minutes ahead but it may stretch up to an hour. There are a couple of fast food-style eateries at the station that will be open. The waiting area is not that comfy. You might enjoy more hanging out in a cafe in the city center until closer to your departure.

Thanks Douglas. Would you mind telling me about your experience on this train? I would love to know what to expect! Thank you.

It's no different than most any other overnight train. Leaves late, arrives early. Reasonably clean and comfy. Not many stops so you might sleep ok. I met pleasant people but their English was limited.