You can only measure in one jib in most classes (all I know). You can replace the battens between races, but there is not much point to it when you have found the right battens (except when going from ultra light to light) in my opinion. The battens are there to let the sail keep it's shape, not change it. Stiffer battens will not flatten the jib substantially in high winds, or will do so only locally and ruin the jibs shape.

The real question is wether the fully battened jibs are faster than partially battened jibs? For mainsails the answer is well known, but they have much more roach and thick masts in front of them. I sailed the Tornado before we got fully battened jibs, and I am not certain at all that the fully battened jib is faster. Getting the right shape into the sail in very light winds is harder in my opinion. and the sail is heavier which dont contribute to a good shape in the light stuff.
The testing done for the olympic multihull back when the ISAF changed the Tornado sailplan had the classic rig actually beeing faster to the top mark than the new rig. This might not be significant as the new rig sails were undeveloped then and the spi-gear add some windage, but still.. Also, I have not seen anything at all about testing fully battened jibs vs partially battened jibs. Perhaps we can learn some more now that the F-18 class is switching?