Hi Hannag,
Keeping your quiver the same has a few benefits as explained by Space Coyote. Flying kites which perform or feel similar will make it easier to adjust into your selected kite more rapidly.
I would suggest not mixing different bars with different kites. Unless of course the bar is a mighty upgrade from your favourite kite. Keeping the bar that comes with the kite will be much easier to sell. Mismatching gear is more difficult to sell and looks odd. Some bars safety systems are incompatible with certain kites as well.
Try keeping your quiver consistent to gain the best progression from your riding.
Buying two kites and a single bar can be a great way to save money (up to $679 for Cabrinha bar

). However, using only one bar all season will put a lot more wear and tear on the bar and lines making it look old prematurely. Also when selling a kite without a bar you restrict your potential customer base and shops will be less likely to want to trade in a bar-less kite. It's also good to have a second bar in case of failure whilst away. 3 kites and 2 bars is a better idea if you can afford it.
DM