" as would like to think the instance will still be up in a decade's time." Only when you pay yourself the hosting, you can guarantee that, at least as long as you pay. How long are the interviews? how much data is it? and what's the topic of interviews? https://fedidb.com/software/peertube check out the different service, look for a big one (they maybe will stay longer? but that's just an assumption) and search who will allow you to upload such long videos. www.yiny.org for example has loooon videos, maybe that's something for you?

@joergi fair point. that looks an easier-to-explore list than the one at joinpeertube.org - thanks for that too.