How long is a leaked Timeout actually leaked?

[FrankReh]

The advice to avoid a Timeout from being cancelled when it goes out of scope is to call its forget method.

I wondered how that doesn't leak memory in the Wasm module, but tracing through to the wasm-bindgen closure module, the call to forget which calls into_js_value and the doc for into_js_value says this does leak memory, and can overwhelm the page if done too frequently.

Is it correct that this is referring to memory consumed within the Wasm module's memory (so replacing the Wasm instance with a new version might be an option for some), or is this referring to JavaScript memory associated with the document?

And projects are fine leaking memory by using forget on their objects that hold closures, or they generally find ways to code around the issue by not using forget and not letting their instances go out of scope?