For longest bloom I'd suggest you research bulbs that bloom at different times so that you get a succession of blooms. For example, crocus for very early spring, then daffodils, then tulips and then work on the summer bulbs like lilies (and I'm sure there are early and late ones). For the latest blooms, perhaps some surprise lilies (Lycoris). A friend gave me some rain lilies and they are just now blooming - very pretty!