It’s a good question. I went looking for an answer. I found this article [1] which claims the long service life owes to an engine and chassis that, while not exceptionally durable, is cheap and easy to maintain.

The article also says you can learn more at llv.com.

Bonus, I learned that Grumman LLV stands for Grumman Long Life Vehicle. Maybe everyone else already knew that, but I thought it was cool.

1 - https://www.speedsportlife.com/2010/02/22/avoidable-contact-...