It has been fifty years since the disk instability model was first proposed.
Extensive observational and theoretical efforts have been devoted to this field.
The physical origin of the instability has been elucidated, the basic outburst behavior of dwarf novae and low-mass X-ray binaries can now be reproduced, and in the field of cataclysmic variables, it once seemed that a unified model for various kinds of transient events and binary evolution had been achieved.
However, recent advances in broadband transient surveys have revealed a number of transient events that cannot be explained by existing models, and the study of compact binary systems is entering a new phase.
It is therefore necessary to improve the disk instability model and to construct a grand unified model capable of explaining the rich variety of outburst phenomena in compact binary systems.
In this article, I review the motivation for organizing the 87th Fujihara Seminar, the history of research on the disk instability model, and what I believe is essential for establishing such a grand unified model.