I just thought I'd pass on my findings of an experiment I've referred to a couple of times. About a year ago I drilled an oil port into the Sturmey Archer hub shell and sealed it with a short bolt and rubber washer. I cleaned out all grease from the srf3 hub except a smear that I left on the wheel bearings. I replaced the greased for life lubrication with a small amount of light oil (10:30 engine oil).
My early findings were that putting in too much resulted in the surplus oil rapidly working its way out of the hub and along the spokes to the braking surface, so I topped it up less often and only very slightly. I find that the addition of about four drops of oil every 200 miles is plenty and that you can probably go more than twice that mileage without any ill effect. I also put in some very fine graphite powder which was intended as a lock lubricant. I reasoned that this would work its way around in the oil and that the crushing of metal contact on cogs and gear rings would smear the graphite onto the metal, providing additional wear resistance if by accident, it ever ran on the dry side.
Anyway - yesterday at just on 3000 miles, I took the hub mechanism out of the wheel and gave it a careful look over without dismantling it from the cluster into separate parts. My conclusion is that the hub is VERY well lubed, all mechanical parts are covered with a good film of oil and the graphite powder has been carried throughout the mechanism. I'd say I can easily cut back on oiling. It's three hundred miles since it was given any and there is plenty in there on every part. I'll wait another five hundred miles without giving it any more attention and then take it down again and check everything out. I should have photographed it and posted the pictures - stupid to think of it now, but it's all back together and has another fifteen miles on it. I'll do that next time I look inside.
As for how the hub works on oil - it's very quiet and smooth. If I spin up the rear wheel by pedaling it on a stand, it keeps on spinning for a long time - pretty much like the front one does. Gear changes are completely slick and reliable. No water or other contaminants have got inside and most of the parts still have their original blue metal appearance. In its fully assembled form, only the tips of the planet gear wheels show shiny bright polished appearance. The ring gear teeth are so lubed up that I can't comment on the surface appearance of them, but the teeth are unworn and well defined.
On reassembling the mechanism into the hub shell it is very important to set the non drive side cone adjustment properly. If it is too tight or lose, the gear alignment inside will be suspect. The online guides explain how to do this right. I find about a quarter of a turn to half a turn back from finger tight, will be about right. The manual warns that more than three quarters of a turn back from finger tight is damaging. The right setting gives just perceptible play at the rim in a lateral direction.
All told I'm glad I did the experiment. I think this hub will last a very long time.