How long it takes for a coat or layer of oil paint to dry to the stage where you can apply another coat depends on the technique you're using. Oil paints can be used wet on wet, thick on thin, or wet on dry. If you're painting glazes, you need to wait until the paint is thoroughly dry, so think at least a day rather than an hour.
Test the paint to see if it's dry with your finger. If it's too sticky, you need to leave it for longer. If you don't give it enough time you will find the new layer you are putting on will be pulling off or mixing with the previous layer. (No harm done, you can always go over it or scrape it off, oils are forgiving.)
The drying time also depends on the oil paint colors you're using (some dry faster than others -- see Which Oil Paint Colors Have the Fastest Drying Times?) and how much (if any) drying oil or solvent you're using.
If you find you're continually getting frustrated waiting for oil paint to dry, try having various paintings on the go simultaneously, so you can swap between them. Or paint those sections you're happy doing wet-on-wet (such as a sky or blended background). Or consider switching to acrylics which dry far more rapidly.