technically, your friend is wasting weed.

It doesn't really "waste" the weed, but when you burn it that fast and you can't hold it in, not only are you bumming your own trip (cause you're coughing) but the weed continues to burn after you take your hit, so that's wasted weed too.

You have the right idea. Corner the bowl, take in as much as you feel comfortable with. Don't worry about your friend. When he goes broke and can't afford to buy any weed, you'll still be flying. (cause you get high either way, his is just more rapid.)

Enjoy.