As pointed out in the answer to this question, a half-elf can choose the favored class bonus from the typical +1 hp or +1 skill point, or take any of the racial favored class bonuses offered to a half-elf. In this case, focused on bard, the options are:
Add +1 to the bard’s total number of bardic performance rounds per day.
Add one spell known from the bard spell list. This spell must be at least one level below the highest spell level the bard can cast.
for human, or
Add +1 to the elf’s CMD when resisting a disarm or sunder attempt.
My question is, could a half-elf (or anyone with multiple options like this) take a different one on each level up?
For example, could a half-elf bard take extra health for the first 2 level ups, then take an extra round of bardic performance (the Half-elf FCB) for the next level up, and then switch to taking the extra spells known (the Human FCB) for the remaining levels?