In all fairness, can you tell the vintage and/or model difference between these 2 Tesla's below?
Both are my cars and I gotta tell you I could not tell (one is a 2013 S60, the other 2015
P85D). From the front, the only difference I can find is AP hardware which was not there in 2013, but that is a small detail only a Tesla fan would be able to spot. We also have a 2017 which looks identical from this angle other than the slipstream wheels and body colored mounding along the bottom. From the front of course AP2 hardware and no nosecone, still not a huge difference.
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True the outside hasn't changed much, but the internals have changed a lot. If you're looking for spare parts for a 1984 Corolla, just about all the parts are the same for a range of years, but Tesla changes parts so often there can be major differences more than once in a calendar year.
I think Tesla does change things too often. They are compounding maintenance headaches down in the future. I read an article about how Germans, Americans, and the Russians made tanks in WW II. The Russian tanks were poorly built with materials that were only intended to get the job done and no longer. The transmissions on the T-34 had a MTBF of 1500 hours and the quality of the welds was often horrible.
The Americans were focused on large quantities of a bit better quality. The build quality was much better and even the parts were often good quality. In the WW II vintage vehicle market American trucks are dirt cheap while trucks from every other country cost a fortune because the trucks were so well made the collecters market is flooded with them. There aren't quite as many American tanks, but that's only because there were fewer uses for them after the war and a lot got scrapped. Even when combat experience showed American tanks were falling behind the curve vs German designs, the US kept making pretty much the same tank because that was the American philosophy of the time. Design something good enough and make a lot of it.
The Germans on the other hand made their tanks a bit like Tesla has done with the Model S/X. They were making changes so often that tanks 3 or 4 apart on the production line could have several noticeable differences. They were constantly seeking the perfect engineering design and disrupting both production and future maintenance to do it.
Tesla is changing with the Model 3 and they will be standardizing production and will probably start doing some kind of model year thing like other car makers. I expect the S and X to get more standardized too. It will make production a lot cheaper.
The problem is if buyers then know when Tesla is going to update the car, sales will plummet in the months before the new version comes out. Other car makers don't have that problem as much because except for maybe 1 refreshed car and 1 all new car, next year's car is going to pretty much be the same as this year's car. And they have sales on left over cars from the previous year in the fall. Other car makers also don't build many cars to order, so they just keep cranking out a mix of car option mixes they think will sell and unload them on dealers.
When the Model S and X are not critical to the survival of the company, maybe they can take a hit on orders between model years. Maybe they will make something else on the same production lines (transport van based on the X possibly? or some other delivery vehicle?) and they will make those when sales for Model S and X are slow.
Right now they need to keep production of the S and X as close to maximum as possible and keeping people wondering when a new version is coming out can be frustrating for the consumer, but it keeps orders in the pipeline.