trade it in for an already broken in car. lol. Just kidding, drive it like you stole it. Then drive it harder.

I bought my Z with 9 miles on it. I babied it the first couple days I had it, but accidentaly went way over 5k rpm's. I am used to shaking my shifter left and right in neutral due to all the short shifters I have owned. I did that on the freeway when enjoying the car and I think it almost redlined due to the syncro rev match. Crappy. Well, after 3 days of owning my 370Z (Anniversary ;-)) it got parked for 5 months (I am a deployed serviceman), I just drove it again because I was only home for a week, and I drove it conservatively for the most part, but definately got on it a few times. I am sure driving it hard before the scheduled break in period will shorten the overall life of the engine, but so will alot of the mods people will do to the car anyways.
In my opinion, follow the break in if you are able to. If you have owned your cars for 5 months like me, have 385 miles on it, and wont see it again for 7 months, well, enjoy your car when you can. Best of luck on whatever decision you make.

As an example I more than followed my MX5 break in procedure. I did not go over 4k for the first 1500km, I changed the oil at 1,000km then again at 5000km with good quality full synth oil. I change the oil every 5,000km and the car pulls better and better. It now has almost 50,000km and the engine feels just like3 it did from day one, I reckon there is bugger all wear in the engine. Treat your 370z like this and it will last forever.
The harsh break in procedure is for morons!

at 1200 i redline at 2.3.4.5 and a little bit of 6..
150mph is dangurous

redline the **** out of it

Drive like you normally would. Go wide open if you want. Just don't hold it at 7500 rpms for a long time. Always wait until your engine warms up and is in operating temperature. Then drive it how ever you want. Do you think when ppl test cars they drive 1200 miles for the engine to break in before they hammer it down. No. Your engine is broken in in 20min. When you test drove your car you stayed under 4k rpms? Not me. I don't believe in break in periods. They are tested at the factory and they redline the motor. You're safe.

haha. you know the new cars that they gave to 'top gear' to test drive, they must all have engine problems afterward because those guys on that show don't baby the cars at all :)

Engine-brake often, don't stay at one speed for a long time, heat-cycle the parts by parking the car for a while (normal driving/stopping, basically, no road-trips).

Most new engines are finished so well that they are broke-in other than the heat-cycling by the time you have the keys in your hand at the dealer. All the micro-polishing and whatnot of the bearings makes long, laborious break-ins a thing of the past.

I would follow the advice aboue 4K/1200 miles, though, if for nothing else because if you got a defective part, they couldn't even try to wriggle out of replacing your engine. Crap happens. 4K rpm in a 370Z is plenty for daily driving. The engine produces a VERY! impressive torque curve profile.

general rule of thumb for this car is, its a sports car. Unless the car is parked, at no point in its life should the rpms drop below 5000. heck even at at red lights i keep the revs up, u know just to be ready.