Yeah it's common.. they stretch like crazy. Most bars have adjustment knots to adjust for line stretch. A lot of old schoolers replace the front lines with Q-line, and save the front lines as a backup set of back lines.

Q-line will last 3 or more seasons...technically forever because you can tie it together when it breaks. Stock china line will last one a season if you are lucky and don't ride a lot, but you'll need to replace the whole set when one breaks.

Problem is Q-line feels like 12 gauge copper wire. But it's great for down winders because you know you can repair line breaks without issue.

One of my front lines stretched after doing a bunch of kite loops... (when looping to the right, the left one stretches). I gave my kite to Bryan, who handed it to Scott, who promptly tried an s-bend... when he looked down at the water, the kite looped full power without warning...

I was a little upset that he was giving my kite a bath

Until I saw how pissed he was because it drilled him like a little rag doll.

Sorry buddy lol. Should've warned you about that stretched line.