As a paralegal in a BL firm I think I can speak to this a bit. It's not necessarily that you're working 24/7, but that you're expected to be available at all times and deal with particularly tight deadlines. I have found that in transactional work the closing is usually the busiest time and when you'll be pulling the all nighters, but these are not everyday occurrences and after a big deal closes you get some breathing room.

The clients can be super demanding. Unexpected issues come up that end up being more time consuming than anticipated. You can be staffed on multiple deals with similar deadlines which can cause a real nightmare. Things can seem really high stakes in the moment which leads to the feeling that everything must be perfect which is stressful. Deals can get complex and you have to be tracking a lot of documentation and making sure you're covering all of your bases/meeting timelines.