I want to make what should be a fairly uncontroversial proposition: if you are giving a talk -whether it be at a seminar or on a panel, in a lecture setting or at a conference - you should keep to time.
I say that it should be uncontroversial, because I'd estimate that at around half of all the academic events I've attended, speakers have exceeded their allotted time, often easily doubling the amount of time they were given to make their presentation.
Whenever this happens, it's laughed off. They give a fleeting apology and then explain that they "just had a lot to say". They acknowledge the chair when they tell them they have five minutes left, then proceed to make absolutely no effort to speed up or bring their talk to a close in good time.
I don't think it's funny. I think it fundamentally shows a lack of respect for the audience, for other speakers, and for the chair. It also shows a lack of skill in one of the most basic aspects of academic work: being able to present information.
What I'm about to say should be incredibly obvious, but I think it needs saying, because apparently the basic concept of timekeeping itself isn't obvious enough.
When you go over time, you disrespect your audience. You tell them that what you have to say is so important that their questions can wait, and if they have other plans then they ought to put them on hold in order to hear you out. You make them uncomfortable, because everyone is aware that you've gone over time but nobody wants to call you out on it. Nobody knows how long you're going to go on for, or if you're even aware that you're doing something wrong. You tell them that your time is worth more than theirs.
When you go over time, you disrespect other speakers. You tell them that your presentation is more important than theirs: that they should be willing to cut their talk short in order to accommodate you. If you've just followed on from another speaker who kept their talk to time, then you've disrespected them because if they'd known that they could have safely exceeded the time limit then they would have been able to present just as much information as you. You tell those speakers that your work and your words are things that need more time to present than theirs, because your work is better or more important or more interesting.
When you go over time, you disrespect the chair. You put them in an awkward position where they have a number of bad options. They could interrupt you in front of everyone, likely angering you and making them look like a killjoy. They could let you keep going, knowing that they're cutting into the time for questions/other speakers/other sessions/lunch, and with no guarantee of when you're going to stop. They could try to stop you, making increasingly desperate facial expressions in your general direction in the hope that you'll notice and wrap it up.
And when you do finish, you put the chair in the position of having to decide whether to cut your question time (which will, again, end with you looking and feeling indignant, and deprive the audience of the ability to question you), or to tell the next speaker to please keep to time (but why should they, when you've just gone over and nothing's happened?), or to hope the organisers won't mind if you cut into lunch.
When you go over time, you disrespect the organisers, because you tell them that their arrangements, usually made under significant constraints, aren't as important as your ability to say everything you want to say. At worst you shift the entire day so that nothing else runs to time.
Fundamentally, it's an expression of power to be able to flagrantly exceed the time allotted to you. You're trusting that you won't be stopped because the chair or the organiser or the audience will feel too awkward to stop you. You're willing to make everyone uncomfortable in order to get through your slides. You put chairs, who are often junior to you, in a position where they either have to call out a more senior member of their department in public or risk the whole session becoming derailed.
It doesn't matter that you had a lot to say. If you're in academia, everyone has a lot to say. Each and every person could talk about their research all day, every day, and they still wouldn't be able to exhaust their thoughts. The point of a talk is that you have a set amount of time to effectively present your ideas to an audience. If you (a) can't present your ideas, or (b) can't keep to time, then you've failed. It is just as much a bad talk if you go over time as if you were boring, monotonous, inarticulate or unintelligible.
Not only are you failing at one of the key skills you should be attempting to master just by going over time, but the extra time you take isn't even helpful. Everyone is looking at their watch, wondering when you're going to stop. They're hungry because you're eating into their lunch time. They're bored because you're unable to be concise. They're tired. Ironically, in taking extra time so that you can present more information, you're making it harder for anyone to take in your presentation.
You also erode our ability to trust other academics. I go in to every talk now wondering whether it will run to time, or whether I'll have to miss the last bit to attend my plans for afterwards. The last ten minutes of every talk are spent anxiously checking my watch rather than listening to the speaker, feeling pre-emptively awkward on behalf of everyone in the room in case you decide you want to take an extra fifteen minutes to get your point across.
And here's the kicker: it's so easy to avoid all of this. Going over time is usually caused by one of two things. Either your ego is inflated to the point where you genuinely think that it's okay for you to spill over into the next person's time (and you were perfectly capable of keeping under time if you so wished), in which case - well, it's not and you shouldn't. Or, you're just disorganised and have too many slides and haven't adequately accounted for how much time you've got to put over the information you want to impart, in which case you should fix that. You wouldn't go in to a talk without any idea what you wanted to tell people and just wing it (unless you're like, Paul Feyerabend or something). Likewise, you shouldn't go in with no idea of how much time you're going to need to say the things you want to say.
Time is the most precious resource we have. Don't disrespect other people's.