Most women who have experienced both claim that it's simpler to have several G-spot orgasms than it is to have multiple clitoral orgasms. When an orgasm rears its beautiful head while you are playing, try whispering some words of encouragement (and possibly ratchet up the intensity just a little bit), but essentially continue pleasuring through her orgasm, later, and perhaps into a subsequent one.
Provided that it feels good for the two of you, what is the point of quitting? There's frequently a"pyramid effect" with multiple G-spot orgasms; every one makes the next one feel better, and makes virtually anything else sexual feel better also.
However, as I said earlier everybody is a bit different, and quality is obviously more important than quantity.
It's true for some girls that G-Spot play may become more likely to result in orgasm over a period of months or weeks after first beginning to experiment with it. Additionally it is true that the high level of G-Spot orgasms could be directly associated with pubococcygeal muscle tone, which is another incentive for performing routine PC muscle exercises.
If you are a girl and you want to try including your G-Spot when masturbating, a really good blend of toys are a vibrator (used in your clit as you are getting warmed up).
Incidentally, in general it's not a great idea to have a massive ego/emotional bet in having (or"giving") orgasms or multiple orgasms; many gender teachers believe it isn't useful to get"goal oriented" about something that's supposed to be enjoyable.