With HTTP/1 the limit is 6 per domain per browser. With HTTP/2 the limit is negotiated between the server and client, 100 by default.

It's not a problem in practice, just ensure to use HTTP/2.

I'd also add even if for whatever reason you are on http1.1 (you should really use http2 for server driven apps there's a lot of other advantages). Datastar prunes connection based on the browser visibility API so on http1.1 a user would need 5-6 visible tabs/windows visible at the same time for you to hit any issues.

Assuming you are using Datastar the way I do with a single persistent SSE connection.

This feature is also much better for the battery life of devices and the server as you are only sending stuff if the user is there.

Not with HTTP/2