Can semen be discharged hours after a wet dream or thinking about lustful thoughts?

The delay in the emission of semen after a wet dream or thoughts is conceivable and happens. If semen is emitted, ghusl (ritual bath) becomes obligatory. However, if madhiy (pre-seminal fluid) is emitted, then ablution (wudu') is obligatory, along with purifying whatever it has touched of the body and clothing. If there is doubt about what was discharged, the person may choose between the possibilities of their doubt.