Prism lines? Maybe not so bad then.
Lines are your only connection to your kite. You can feel it, little gusts, lulls, how it reacts, better with them. Higher end lines also don't stretch as much during flight, again giving you better feel. It might not be quite as important on a foil, but you will definitely feel the difference on the framed kites.
If you flew a lot on the original set - quite possible you might have nicked them and they failed due to that. Or they may have just simply worn out. I have older lines I still use today. But I'm careful to match kite and lines to my wind. Look at the lines - are they fuzzy looking? Probably fairly worn. Especially at the point the lines cross each other. Better lines use a tighter weave and handle the "crossing" .
As with most things - let your budget be your guide. But try to get the best lines you can afford.