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