User Property History

User property history means keeping the sequence of values a property has held over time, not just its current value.

Most tools keep only the 'value now' for each user property; when a user's plan moves from free to paid, the previous value is erased. User property history changes this and keeps every change with its timestamp, opening the door to 'as-of' analysis: you can ask what attributes users had at the moment of purchase, not what they have now. Its importance is in lifecycle and cohort analysis; without history, any breakdown by a changing property becomes misleading, because you see the past through today's lens. Its cost is volume and complexity, which is why most tools do not provide it by default and only have a current-value view. This feature needs a model that even has a writable user property in the first place.