The chain on my summer bike is a Rohloff SLT99, running on Dura-Ace 9 speed (7700) components.
I think I have got my chain lube routine correct when you consider the following...
Being installed on a summer bike, it is fair to say that the chain has never been subject to salt etc, perhaps the odd wet ride, however the bike was my good weather training bike when I raced; I stopped in 2016. The bike has been used in hill climbs and subject to other extreme high level efforts, so it is not as if it has had an easy life. One training ride I did, which was totally insane, and undoubtedly put huge strain on the chain was riding up a local 1 in 10 hill in 53x13 at around 15rpm!
The chain is probably about ten years old, at guess that would equate to around 40,000 miles.
The chain is now showing a slight amount of stretch, I think it will be good for around another 20,000 miles, which apparently is quite a lot for a bike chain, but actually quite normal for these chains, which if you know your chains are regarded as one of the best chains ever made.
However, I think part of the reason why it has lasted so long is down to my maintenance routine.
What I do is when I clean the bike, the chain gets completely and totally cleaned to the point that there is no residue on it; i.e. I can run the chain through a clenched fist and there is virtually no oil on my hand at all.
I use the Rohloff chain lube which seems perfect for the chain. I apply this lube very carefully, ensuring it only goes on the rollers.