Sometimes, you have to know when to get out to end on a high note. American television is notorious for this. Game of Thrones and House of Cards are recent examples. The American television industry is the one that gave rise to the proto-meme of "Jumping the Shark." (On the other hand, the Japanese anime industry is notorious for often leaving people wanting more.)
On the other end, Apple's biggest successes involved knowing when to wait, and when to move, so that they didn't release something which wasn't ready. Apple didn't release the first MP3 player. They didn't release the first smartphone or the first tablet.
So I doubt that Amazon is "done" at 2 day delivery. However, given my experience with new Amazon services, I'd say that they've created an incentive structure for internal groups to be first, even when they're not ready to the point where they somewhat damage the brand.
Product differentiation for the sake of differentiation is always a dangerous game. Someone posted here the other day about "peak products" where the product reaches an ideal state which is an interesting concept!
The problem is an obsession with constant newness misses stuff like privacy, customer support, longevity, etc. But they care more about having a new flashy SKU for next season which looks different.
Edit: the Wikipedia for "Jumping the shark" is excellent, apparently from when Fonzie jumped over a shark in water skiis as part of a promotional gimmick on Happy Days. https://en.wikipedia.org/wiki/Jumping_the_shark
if they had ended in season 5 with the material already written, none of the storylines would have been resolved. therefore, some amount of additional story had to be developed, so if you're doomed to disappoint fans, why not write 3 more seasons and make a bunch of money in the process? in a deadline-driven environment, no army of writers was going to produce a satisfyingly detailed and consistent ending to match martin's prior work (it seems even martin himself is having trouble with regard to the book series).
No one was locked in. You know what the Japanese anime industry does in this case? Sometimes, they draw out the story, so that entire episodes are taken up with just powering up. (Dragonball Z) More commonly, they just wait for the author!
Of course, the anime industry has the advantage, that the "way someone is drawn" can remain the same after a gap of 5 or 10 years, while human actors age. However, in 5 or 10 years, I don't think that's going to be prohibitively expensive anymore.
Was there something before the Newton?