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**Do you want to request a *feature* or report a *bug*?**
Not sure if its a bug or a feature request.

**What is the current behavior?**
The component given as a fallback to Suspense is remounted each time a lazy child resolves.

https://codesandbox.io/s/z6v6x3n1np
This example shows how a fallback component, which counts up, is mounted more than once.

**What is the expected behavior?**
The fallback is mounted once and is only unmounted when all lazy children are resolved.
In the example the counter would run up to 9.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
react@16.6.0

state = {error: null};
      componentDidCatch(error) {
        this.setState({error});
      }
      reset() {
        this.setState({error: null});
      }
      render() {
        if (this.state.error !== null) {
          return <Text text={'Caught error: ' + this.state.error.message} />;
        }
        return this.props.children;
      }
    }
    const errorBoundary = React.createRef();
    function App() {