I found out yesterday that I have an oblique fracture of the 4th toe. I am elevating and icing it. How long should I expect this intensity of pain?

Depends on your body. Bone takes approximately 6-8 weeks to heal in the average healthy individual. But as mentioned in other responses, the worst of the pain should subside before then. Rest, ice, proper compression and elevation should all help reduce your pain level. I would recommend speaking to your healthcare provider regarding anti-inflammatory or pain medication if the pain is severe.
Are you walking on . It? You should have a surgical shoe at minimum. Not sure what the intensity level is that you have but you can try Tylenol (acetaminophen) and see if that helps in addition to the icing.
Fractures heal. Frcature can usually heal in 6 weeks but your pain will not last that long. We have no ideal of yousex or age. Ask your physiciasn or hav eyou see an orthpedist.