I've talked about this a few times with a number of people in webtoon communities (largely readers) because I've also thought about it a lot. From my experience, general consensus is that a haitus over a month is too long, and people will often drop the story at that point. I'm kind of in the same mindset, too. If it's been over a month I'll probably get annoyed and drop my sub.
I do actually think it is the responsibility of a creator to finish their work. That isn't to say it's always possible, and things do happen. But I think when you decide to do something you should finish it. Don't set unrealistic goals or timelines, and try to only do what you are actually able to. But I do think it's irresponsible and disrespectful to readers to just drop your work or randomly go on a hiatus for an undetermined amount of time. I'm well aware this is also a general consensus among many readers out there and I have seen a couple creators who've basically destroyed their reputation from that exact sort of thing.
If you just randomly need a break and it's unplanned, I would let people know you will be back in x time (for me, more than a week is too much. But I think a month is acceptable in general). But it should be a kind of rare thing. I think it's much better to have a 'season' for your work, where at the end of each season you take a designated hiatus. I think readers tolerate that much better.
I have a chronic illness and I've been very forthcoming to my readers that it can potentially set me back, but that's also why I have a backlog of episodes.
Edit: I've never gone on a hiatus, but I genuinely enjoy working on my story and I'm used to spending years actively on a single project. But I also wouldn't set up a story I can't finish (reasonably, of course).
Edit 2: After some consideration, I'd also say this isn't actually the best place to figure out what the average reader is and isn't okay with. Obviously people are going to respond with their own needs, experiences, etc as creators, but that's a hell of a lot different than your average reader. Knowing what it is to be one can have a big impact on your views. So I'm mostly speaking from what I've learned asking the general community (not here, because this forum is almost entirely creators. I mean people who just read comics. Average everyday readers). And it also depends on how seriously you take your work. If you see it as a hobby or more. I see it as more than that.