Comment 8 for bug 1747708

'since' seems a poor name for 'last time the charm told us its status'. If a charm has been 'active, live master' for several months, I would expect 'since' to show me several months, rather than always <= 5 minutes on a normally functioning unit and 'active, live master' with a larger 'since' indicating a failure somewhere. The current behaviour and naming makes it look like things are flapping when things are good and stable when things have failed. Maybe we need a separate timestamp for the 'keepalive', if people make use of it. FWIW, juju-wait uses 'since' as part of its heuristic to determine stability of an application and will fail if someone sets the threshold higher than the update-status frequency.

I imagine if we change things here they can't happen until at least 2.4, since it would be a behaviour change rather than a bug fix. For now, I'll need to cache the last seen change delta for every unit and application to detect if the model change notification actually represents a model change or just a keepalive to be ignored.