If you're mostly flying around the Southern Hemisphere, hotel and food prices can be very very cheap. The price of a night at an ordinary 4-star hotel in London or Tokyo equals that of 3 nights at an equivalent 4-star hotel in Montevideo, and will probably keep you for over a week in a lodge in rural Thailand.
If you can save a couple of thousand dollars on a business-class ticket, that's most of your stay paid, while getting a boatload of miles into the bargain.
If you're just spending miles on a leisure trip, I agree that a couple of weeks sounds way too rushed...but FTers are known to travel a lot, so you may want to do it quickly in order to get a feel for which places are worth returning to...