Most adults have 50-200 casual acquaintances and may know hundreds more by name. The inner circle of 3-5 deep relationships — the people who would help you in crisis, who know you deeply, who you call first with good or bad news — is what produces relationship-based wellbeing. The rest is nice; it doesn't replicate the inner circle benefit.
Who belongs in the inner circle
People who've earned trust over years. Mutually invested. Available emotionally. Different demographics often (partner, best friend, sibling, mentor, specific friend) rather than five copies of the same role.
How to maintain
Regular contact (weekly minimum for most). Show up for important moments. Invest energy proportional to the importance of the relationship.
Most adults under-invest in inner circle and over-invest in periphery. Reversing this produces noticeable wellbeing improvement.