Title text:
"How does the spring not run out almost immediately?" "We pull it back REALLY far."
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3244/
Bcz springs wear out is my guess. That's the first thing I'd worry about in the design is how many cycles can it handle before performance is degraded. Might be a lot, but even if it's a couple years, people aren't going to be happy when their car performance suddenly drops off right after they finish paying the thing off.