This isn't a color topic, but...
Re longevity, the picture is pretty complex. To oversimplify, the available evidence suggests that with current Kodak selenium toner, you really need to tone to completion to get full protection. The 1+20 or 1+40 for a couple of minutes that many B&W printers have traditionally included in their workflow has limited effect. The problem is that toning to completion with selenium generally produces results that, to my eye at least, look really ugly.
Like FB, RC is subject to the same general vulnerability to having the image silver attacked by atmospheric pollutants. But RC has another mode of deterioration that doesn't affect FB paper: light-catalyzed reactions between the image silver, the titanium dioxide pigment used to whiten the paper, and the polyethylene coating. These can lead to cracking of the PE surface and/or gross silvering-out and discoloration of the image itself. For some years now, manufacturers have included antioxidant compounds in RC papers that suppress these reactions, though how long the protective effect will last is unclear.
In addition, in an experiment a few years back, Ctein demonstrated convincingly that relatively modest toning with selenium can at least prevent the sort of very rapid deterioration that can sometimes be seen in RC prints that are framed and put on display just after printing. The degree of protection over the longer term remains unclear.
In Ctein's tests, Agfa Sistan also showed a protective effect on RC prints. Sistan is a silver stabilizer that's used as a post-treatment for any silver images - RC, FB or film - and has no effect on the appearance of the image.
It's also possible to use a combination of selenium and Sistan, the former mostly for appearance and the latter to protect the image silver that hasn't been converted by the partial selenium toning.
My own practice at this point, most of the time, is to treat FB prints with Sistan for protection, and to tone RC prints for appearance and for some protection.
FWIW, some RC papers react very strongly to selenium toning, just as some FB papers do. For example, Ilford MG RC Warmtone, with a minute or two in Kodak Rapid Selenium Toner 1+9, produces very, very deep blacks. Further toning results in radical color change toward browns and reds.
If you must have complete protection of the silver image, sulfide toners are more effective than selenium. But they're quite noxious and a nuisance to use, and substantially change the appearance of the image.