This is a question that plagues me. On the one hand, I have been told that conference papers do not a tenure case make. On the other hand, going to conferences enables you to meet people, perhaps impress them with your well-composed talk, and network, which does affect your ability to create a list of external tenure reviewers. For non-tenure-track folks, conferences also introduce you to people who might write letters for your job application or who might be in a position to hire you. So how many a year?
I sometimes wish that we gave papers like figure skaters or gymnasts delivered routines. You make one great paper per year and then go around delivering it to various audiences. Given how small many conferences are, this practice would perhaps be most useful. But given that we live in a different world, we can't (though people who have strategies for writing the same paper beneath different titles should chime in). So how many a year?
I say 2 or 3. Others can contradict me. But I also want to pre-warn interdisciplinary folks. I have gone to multiple conferences in the past year and I have never encountered audience overlap. A variety of perspectives is good, but you also need to establish a reputation in your primary field. Be strategic.
Medievalism, and migration
5 years ago