Chances are, ivory will move over time. If it has sat for a few years in a humid area, and then is moved to someplace that is dry, it will shrink. That can cause cracking, and you can end up with spaces between bolsters and handle material. The shrinkage can also make it so that you can see and feel the edges of the liners that have become exposed by the shrinkage. If you go from a dry to a humid area, the ivory will expand. This can also cause cracking, and where joints used to be smooth there will be a bump when going from the bolster to the ivory.
The other problem is that ivory isn't very impact resistant. Bark mammoth ivory, with all its natural fissures, may be the worst ivory for having this problem. Be careful not to drop the knife, and don't bang it into anything hard.
Makers that have experience with ivory have little tricks of the trade that they use that can reduce some of the problems caused by ivory moving. You can do things yourself that will lessen the problem, but it is next to impossible to get rid of completely.
Even with the problems mentioned above, ivory is my favorite handle material. I understand the problems it will present to me and am willing to accept them to get the beauty this material delivers. I have never had any cracking, chipping or breakage happen, but have some ivory that has shrunken slightly.