This work is motivated by the strong demands of flash-friendly index designs to resolve reliability and performance concerns for data manipulations over flash memory. Different from the past work, we propose and explore the impacts of hot-data access and sibling-link updates to a tree index structure over flash memory. In particular, a flash-friendly B+-tree, referred to as a Durable B+-tree, is proposed to not only improve the endurance but also the performance of a tree index structure over flash memory. The capability of the proposed methodology and index design was evaluated by a series of experiments, in which significant improvement on endurance was achieved, compared with the past work.