This is regarding my findings in the following post:
WCF and OneWay – Behavioral Inconsistency
The best practice remains the same - calling O/W operation should end the use of your proxy object.
However, the next suggestion that I made - calling abort - is a bit tricky.
We found that once in while a single call would yield an exception on the server side and the execution on the service never happened.
The client never received an exception (because it's O/W) but we were able to see in the server logs thanks to our error handler logger.
That happened about once every 600 calls.
So, taking everything into mind - You shouldn't abort the proxy after calling O/W operation (that is when no exception occurs) but you should really call BeginClose with an acceptable logical timeout.
This would suffice with the communication requirements plus give you the fire-and-forget semantics. (once the message is dispatched to the service)