Your kite puts a huge amount of stress on your kite lines .. they're rated at 200kg for a reason.

Overtime, your lines will stretch due to the tension, and there's a strong chance they won't stretch evenly.

Because it all happens so slowly, it's easily overlooked.    At the start of the new kitesurfing season, and half way through, it's a great idea to lay your lines out and ensure all is well.

This great video from Jason & Christian explains it all ... 

How to tune your line lengths: