I don't believe the size of a ferret has anything to do with other
health or genetic problems. The average age of my crew including the
larger hobs and jills is around 8 to 10 years. The oldest being 13. Of
course all ferrets eventually get old age issues but I haven't seen
anything abnormal in the larger ones. Breed ferrets with genetics prone
for certain diseases and that is what you will get regardless of the
size. A reputable breeder is going to trace lineage and disease issues
and will stop a line that shows illness history.

[Posted in FML 6885]