2006 chevy cobalt fuel lines

i have a 2006 chevy cobalt 2.2L L4 i was told that the fuel lines are rusted
and need replaced. i've looked around and i know you can repair the lines
where its leaking, which is a lot cheaper. My fuel lines are not leaking
anywhere just rusted, so can someone tell me if its safe to wail until it starts
leaking and just repair the section where the leak is coming from. mechanic
said $500-$600 for parts and labor, is he just trying to get his money or is it
necessary to replace the whole fuel line?