I will gaurantee my plants for 6 months for any death.
Except in two cases. The first is dehydration - not watering it! I will still replace the tree(s) for 50% off. The second case is indoor stress. No plant I sell will survive 3 months inside a house. Thus I will not gaurantee trees kept indoors.
The number one cause of death in bonsai is the bonsai dehydrates in the hight of summer. This is completely preventable by shading and careful watering.