It depends on the age of the tack, I'd say.
When I got my new Beval LTD2 saddle, I oiled the crap out of it. I was nervous, at first, because I had heard that too much oil was bad, so I was very scarce. Then, my trainer said I should just oil it daily, and I did. The results were great. I just slapped on some Neatsfoot Oil (pure stuff- I'm pretty sure the compound does not rot stitching, though, just darkens faster) My saddle broke in much faster and got a great color.
I'd say if the saddle isn't new, though, don't oil it more than once every couple of months, and don't apply so much oil that it's running off. I like the idea about wiping it off after a few hours-- I can't tell you how embarrassed I was to find my butt was brown after riding in my saddle! Regular cleaning and conditioning will help imbetween oilings. I use Lexol and Passier Leaderdebalsam (sp?). The Passier stuff is a bit pricey, but it smells wonderful!