Currently folders that are up to date are shown like this:

However, the second folder has not been syncing for at least a year!
A problem that is not directly apparent from the overview. Only after inspecting the list of devices synced with this folder and then opening each device to look at the "last seen" value might it become clear that this folder has not been synced in a long time.

To help get trustworthy status update at first glance (something that instills trust in Syncthing) I suggest the above to be changed to:

The threshold for when a folder is considered possibly stale could be some high value by default but editable in the advanced settings of the folder. Let's say a default of 14 days as not all use cases have at least 1 devices online always every second. However, if a folder has not synced (not seen a single device) for weeks; I'd consider that something most people would want to know.

Update: This warning would align with the other similar orange warning when Syncthing knows it can't ever be synced: