That is my own experience say: a week is a good time for the oils set (specially in autumn or winter). It is not a math rule, but is better be sure, because if you paint or varnish over not setted oils, perhaps the paint/varnish will crack.
Beside, it depends too of the solvent you use: white spirit set faster than turpentine.
Some modellers, including me, used to put the oils 15 min or so on a piece of cardboard or kitchen paper before use; this reduced the oiled part of the paint and help the paint not be so shiny.
I hope my spanglish was good enough to get me
Cheers
Darío