I don't think that blossom is running as demo. Primal uses them as default.
I dont think there is any cap on videos on primal but I could be wrong best to ask nostr:npub12vkcxr0luzwp8e673v29eqjhrr7p9vqq8asav85swaepclllj09sylpugg
Most free video services are capped in file size. I think nostr build integrated with some clients and allow up to 4mb file sizes - or maybe they increased that? I don’t remember. Paid nostr.build plan does allow for much larger file sizes.
In terms of blossom servers I think those are mostly demo. Primal does have one but I’m unsure of caps.
Discussion
Is it not the point of blossom to have fallbacks? What good is a single server without a fallback?
Yes, that's why you can also setup mirrors in Primal.
https://primal.net/miljan/decentralized-media%20hosting%20via%20blossom20blossom