I'm inclined to think the opposite: the Enterprise-B was the long-serving starship with the name and was around long enough to be properly decommissioned. The Enterprise-C, on the other hand, was around the shortest, IMO.
Why would it have been decommissioned? We see other Excelsior class ships decades after when the ENT-C would have launched. Clearly, it was a sturdy class of ship that could last nearly a century.