General confessions are not done so much for their sacramental value as for their help in giving you and your confessor an accurate look at your spiritual development over your lifetime. Keeping that in mind, it should not be done by people who are scrupulous or who struggle excessively with despair. They do have sacramental value, in that they do provide grace- but they should not be seen as something needed because previous valid confessions weren’t good enough.
General confessions are particularly valuable tools to help people prepare for significant changes in their lives, such as marriage, death, death of a spouse (especially one you were married to for many years), ordination, profession of vows, and significant anniversaries (10, 25, 50, etc.) of those occasions. Graduation, retirement, a significant change in employment after having worked in one place for many years, moving far away from a home you had for many years, and anything else that happens that clearly will take your life in a new (and perhaps unexpected) direction are also occasions where a general confession could be useful.