That's totally up to you. Typically, women can have multiple orgasms. Once you get them there, and you're still "hitting the spot" they can ejaculate within a short period of time. For guys, we typically need a few minutes.
Immediately. Sperm is constantly being produced in the seminiferous tubules of the testicles. Although it takes 60 days for a sperm to mature from a germ cell, this is constantly being done. Just...
If you find he ejackulates too quickly you might want to give him oral sex before the two of you go for intercourse. If he ejackuates on oral sex for sure he won't ejackualte so quickly during...