BuffBill:
Exactly if you can switch from Titleist to WGT then you only have to be able to switch from one type of titleist to another. Further, WGT does not always warn you or give you an opportunity to reload. This makes the situation more frustrating. You come to rely on being able to reload in game, then all of a sudden no option and you are playing a WGT ball with $100 worth of balls in your bag. Sorry but this is really greedy.
There is a small meter on each ball usage/life in the game and there is also a warning, something like "last hit, last ball, buy now!" You can buy a like sleeve right there in the middle of the fairway.
If you hit your last ball OB or in the water, then you won't see the warning. But you did get a "last ball" message. All the warnings are there if you pay attention.
Like most said here, be a boy scout, be prepared. Stock enough reserve so this isn't an issue or be prepared to use the house ball.