I for one can't believe that there is such a directive ! In all my years of wrenching,I've never heard anyone talk about this changing of lines @ 4 years.
The manufacturers have all been going to this recommendation and there actually is something to it from their standpoint. Beyond the lawyers and profit of selling more parts.
To get more efficient, engines are more tightly packed in and engine areas are running hotter than they used to. We also are assaulting the rubber with more oxidizers from pollution, ethanol, etc than we once did. Onto that mix, the manufacturers have gotten better at understanding that people actually remember which cars they had trouble with and tend not to buy from those makers again. So the maintenance programs have actually gotten better and suddenly they care about being pre-emptive in changing out hoses before they leak, rot, or split.
Does this mean that you're going to hell if you don't do like they recommend? Of course not, but your potential for leakage probably goes up a few percent. It's your bike and it's shades of gray, so you get to decide how far to go in your maintenance.
As for the new brake lines, I just put on a set of Spiegler's and the difference was not huge but the lever is perceptibly less spongy. Since you have a 2004 like mine (non-ABS), I'll make you a deal and save you a few bucks. I happened to end up with two sets of front lines, so I have a spare brand new set with the outer color in black. HOWEVER, the second set doesn't have the hardware, it's just the lines. I'd think that most bike shops will have some hardware in their spare parts bins, or you could see what the harware costs new. Shoot me a personal message with a reasonable price and they're yours.
Bob