COM object lifetime is subject to Windows rundown policy (6 minute idle)

[jeffschwMSFT]

Call CoMarshalInterface with MSHLFLAGS_TABLESTRONG (as opposed to MSHLFLAGS_NORMAL) to avoid COM rundown timeouts.

https://github.com/dotnet/coreclr/blob/8e48db2c113052ef18cdafb43e114a8633864ec0/src/vm/comcache.cpp#L178

The lifetime issue tends to hit very large applications. Viable workarounds are: 1) use the COM objects regularly, or 2) avoid the .NET COM cache and get the raw IntPtr then call GetUniqueObjectForIUnknown.

[AaronRobinsonMSFT]

An alternative to this would be leverage the GIT or IAgileReference type - depending on platform support.

[AaronRobinsonMSFT]

Changing the built-in COM support semantics is something we are attempting to avoid. A source generator with needed semantics could be create using the ComWrappers API if this is causing issues.