What you will find is that you do not get every upgrade that you request as a Platinum. The most desirable flights to upgrade are long flights in 763s, flights with meals, and flights which come the closest to the sticker limits of 550, 1050, 1550, 2050, and 2550 miles without going over. The least desirable are short flights, flights without meals, and flights that are just over the mileage limits. The less desirable flights are easier to upgrade than the more desirable ones. Work with it a bit, try for a few upgrades, see how it goes. If you need to, buy a few upgrades.