when its brand new i oil it over a period of about 2 days, to get it nice and supple.
now i just oil it occasionally, once every 2 mnths maybe, unless it gets wet, and then it gets oiled.
i clean it with saddle soap every time i ride. think the oil i use is hydrophane, its in a blue tin, and very good!! well i think so
I oil the underside of the saddle pretty frequently as it keeps it supple (I use neatsfoot oil). Never oil the topside unless you like that skidpan feeling !! I only oil bridles when they are new to soften them up, and then use glycerine saddle soap after that.
i oil brand new tack only, otherwise i use Effax, which is by far the best leather treatment i've ever found.
neatsfoot oil rots stitching, if the stitching thread is cotton... worth bearing in mind.