Does it help with the life of the output shaft?
My belief is that output shaft wear is directly related to chain tension. And, to be on the safe side I'm only using Honda CS sprockets. I have no way to test the hardness (Rockwell number) of the "hardened" aftermarket sprockets so I'm hoping that Honda is smart enough to have made their CS sprockets just a bit softer than the shaft. No way to tell with the others.
I think that's the best you can do other than just keeping your eye on it.
On chain oilers:
I built my own (cheap) version chain oiler and after 2 years of use I think I can provide some information.
When compared to my son's Transalp ridden in almost identical conditions my conclusions are:
Chain oilers do NOT significantly improve the life of a high quality X-ring chain as long as reasonable lubing and care is taken of the chain.
Where the chain oiler did make a significant different is in the wear of the sprockets. My CS sprocket lasted about 1.5 times as long as the manually lubed bike. My rear sprocket still looks almost new after 2 chains.
The disadvantage.....the chain oiler makes more of a mess. You'll get lube splatters on your spokes, rear tire and rim and a bit more goo around the CS sprocket. This is not a problem and it easily wipes off with a rag. It does help to preserve the finish of the rear spokes. It's also nice to just reach down and turn the oiler on after a dusty gravel road rather than fooling around with spray bottles and cans of lube at fuel stops.