> For example Jai and Odin both seem to really want you to write code which can throw away a "per-frame" arena periodically

You can generalize this far beyond per-frame semantics. Think per-http-request, per-pubsub-message.

Per each, you can create a new virtual.Arena, set it as your context.temp_allocator and use it for the entirety of the request or message. Afterwards, throw it away.