Bored@work, I see where you’re coming from, and understand that 8 years of support may not be out of the picture. So let me approach this differently:
Try to maximize your potential. Do you have any vocational training (you don’t have to answer, just bouncing this off for you to think about)? Anything you might be interested in training for? Assuming you’re in the NY area there are many different options that will help you increase your income and maybe give you some satisfaction too. You may not want to start a 3 – 4 year program but something up to 18 months or 2 years is realistic. Even if you get married in the middle your parents will probably be able to help you while you’re in school and you’ll finish early enough not to have too many family conflicts.
It is very possible you will be set up with boys from something of a privileged background too. I’m sure your parents will do more than adequate research but you assess for yourself if they’re indulged (not necessarily bad, something that as they mature they’ll outgrow – this is where you might fall) or spoiled (not good – and I think you have what it takes to grow in life, so I wouldn’t put you there). Be honest with yourself about what you need personality-wise, what you admire, etc. For example, you may need a sense of humor, you may like a well-rounded boy, etc. Take your time.
And I think you should start shopping for your own toiletries. Not so that you should make dramatic changes like I suggested but just so you’re aware of what the real cost of things are. This will help you be a bit more resourceful when you have to start to make your own decisions and prioritize. (And if you want to live on the wild side, maybe your mother will let you look at Macy’s 😉 But the point is, know that these are options. When you are on your own, even if you are being supported, you will be doing the spending yourself, and being aware of the options will go far. After a few years you will probably suprise yourself with the new, and good, habits you’ll develop.