Second Question: Expiring or Short-Lived Assets Is it possible to put an expiration date on an asset so that it's materialization is automatically deleted after a set period (or alternatively when all downstream assets are materialized)?

This is an interesting thing to think of. I don't believe so. Assets are conventionally thought as things that are persisted in storage [and implicitly stay persisted]. However, an option is to use assets for everything persistent, and everything with a TTL/max use policy can be generated with Ops instead.