I get retiring the class: no more ships built, but seems odd to retire all Connies, just because they're not going to build more of them. Just let each ship reach it's natural end. I didn't stop driving my car when it's make-model stopped being made.
Okay, I'll admit I'm feeling a bit frustrated now, because it seems like you didn't actually
read my post. I did NOT say "just because they aren't going to build more of them." I said "because they had a unique logistical need." Your reply fails to acknowledge that difference, and that makes me feel like you didn't pay attention to my suggestion.
Let me say this in annoying levels of detail. :P
In the real world, various air forces and airlines have retired perfectly good aircraft designs en masse because some spare part was no longer being made, or because it used a unique type of oil, or whatever. These are
organisations with dozens to hundreds of aircraft, and a
huge cost to their business or military operation if an aircraft is not flyable. As in, people might die. Which means they won't fly an aircraft if they don't have spare parts available for it.
Having one aircraft design that needs a part that no other aircraft design needs makes supplying those parts harder and more expensive. They need to be built, shipped, and stored, and for the organization to be efficient they need economies of scale on the logistics side. It's not unknown for an air force or airline to decide that supplying those parts isn't worth it any longer, and retire the entire design in a very short period of time. Because then they don't have to store that one weird part, and they also don't have to worry about their plane falling out of the sky from a shortage of spare parts. And when this happens, sometimes the very newest examples of the thing being retired aren't very old and are still in great condition.
You handle your personal car very differently, unless you're an extremely unusual person. You probably don't store spare parts. And you certainly don't pay for the entire logistics chain - not directly, anyway. The company that sold you the car has taken on the cost of producing and storing spare parts, and has agreed to keep them in stock for a certain length of time. The cost of those parts is partially built in to your purchase price, sure, but it's not an ongoing expense you can just get rid of; and the company has agreed to supply and store those parts for longer than they expect you to keep driving the car. And, for the most part, if something goes wrong on your car it's an incovenience, not life-threatening. So you can afford to keep driving your car even after parts are hard to get, because if something goes wrong you call a tow truck, lose a day's work, and then rent a car for a fortnight until you can buy a new one. You're able to ignore most of the cost of keeping your car operational because someone else is maintaining a supply chain for you and because the cost of not being able to get a part is relatively small.
That's not true for an air force, and it wouldn't be true for Starfleet either. So it's really not that hard to come up with scenarios for why all the C
onnies would get retired in a fairly short time frame. Maybe their warp drives need some component a
Miranda doesn't. Maybe those super thin necks were proving to be a really bad idea after all. Who knows?
This is, to be sure, entirely speculative and head-canon. There's no requirement for you to accept it as part of your own head-canon. But it's easy enough to make "lets retire every
Constitution-class at once" a reasonable decision, if one
wants to.