At least the OG 1701 got a good lifespan - it was no Miranda, but 40 years is great for an Enterprise.

The decommissioning of the A seemed a bit premature, though, considering it was a new ship that was relatively salvageable. Maybe its battle damage was just too much and that’s why it was given to the museum. Alternatively, the A was originally a different Constitution class undergoing a refit was was already quite old by Undiscovered country.

There’s a good chance the B lasted a long time too, though there’s no canon source to its demise, only that it’s not in the fleet museum.