If it's web content, go right ahead. We have many very large sites using the free plan. From your use, it sounds like you're using a CDN for file distribution (i.e., sending out large package files), not traditional web content. CloudFlare isn't designed for that use case. We're also not setup for streaming content (e.g., if you're running a streaming server for video). In both those cases, you're likely better with a traditional CDN. However, if you're using us for traditional web content, there are no bandwidth caps even on the free plan.