Hi Joseph,
The rate limits for app-only auth are meant to solve more basic use cases. In API v1.1, the best way to expand your use of the API to meet your user demand is by requiring users to authenticate and leveraging their access tokens when making requests on their behalf. You’ll then have their rate limits to work with, each isolated from each other. You’ll also have what’s left over in app-only auth to handle sidecar use cases. In this case probably, your “user” is some representation of each event itself.
You’ll also want to look into the Streaming API. Instead of repeatedly issuing the same recurring queries for a conference or event, you would open a single longer-lived stream on behalf of all your events and receive the tweets matching in real time. Then you bucket them by event after processing.
Using the REST & Streaming APIs together is the best way to be flexible in a scenario like this.