Every high-end sports car that represented a major technological change from the previous generation has become a collector's item worth much more than it sold for new. There are no exceptions to this rule that I'm aware of. There aren't very many - less than 10 examples that fit this bill. The Roadster is the most recent one.
Not sure but there's a well documented phenomenon that has been observed. Those who can afford the car will buy it right away and get the desire to own it out of their system. The younger generation who most adores the car when it is first released often cannot afford it at the time. Later in their lives they are often more successful and then start lusting again for the same car they dreamed of when they were younger. That's usually when the collector's market takes off. Unfortunately it's usually kind of slow.
I would say a minimum of 25-30 years pass before the cars really appreciate in value. It takes less time for very limited production cars, but they are usually very expensive to start with. A good example of that former are most pre 1972 muscle cars, and the latter scenario makes me think of the 65-66 AC Cobras.
30 years is a good number. Same for other collectibles like toys, kitsch and retro. 30 years is fours cycles of fashion.
From the article: This guy must have some impressively large luggage. And his future AA sized/weighted battery will make this question more reasonable: