Hey there!
I've heard people mention oiling the leadpipe for this particular reason, but I've never put much stock in it myself. Red rot is a form of corrosion. There are apparently still competing theories exactly how it happens, but everyone seems to agree it is caused by exposing the metal to a slightly acidic environment over a long period of time. Ergo, the best way to preserve brass should be to keep it clean and dry when in storage. If you have acidic saliva or sweat, you run greater risk of red rot, but it should be very possible to mitigate it by simply cleaning it more often than others.
If you're really worried about this antique, maybe do a leadpipe swab after each play session, followed by a wipe down with a soft cloth. No horn will rot if it's clean and dry.
I suppose the argument for oiling would be that the film of oil will stick to the inside surface and prevent acid (hydrophilic) solutions from sticking there. I don't know if there's anything to that theory, but my experience as a mechanic says that if you add oil to any place that's exposed to air, that surface will start collecting particles (dust). And once you have particles stuck on a surface, those particles will absorb humidity, which means you now have an oily, dirty and wet surface. I'd say that's a red rot waiting to happen right there.
An engineer would say: lubrication goes directly on bearing surfaces and nowhere else in the machine. Other surfaces should be clean and dry.
All this said, I don't swab my leadpipe. I do empty out all slides when I get home after a rehearsal or gig, and there's usually plenty in there once the cold night air has condensed the humidity out of the last breath I left in there. I clean as often as the next guy (every few months). I always rinse out my mouth or brush me teeth before playing. Never suffered red rot in one of my horns yet.
Certain models seem very prone to red rot. Kanstul "Besson Meha", older Benges, the Yamaha Miyashiro model, for instance. You might have to be extra careful around one of those.