Sennheiser HD 700s need a lot of break-in?

Just received a pair of HD 700s today and I am pretty disappointed by the sound. It's very dull and closed sounding. Not what I expected. My 10 year old HD 600s sound far better right now. Those do have the Cardas cable but that can't be the sole reason. Does anyone have any experience with the HD 700s? Maybe they need a lot of break-in time? Any help is greatly appreciated!
I don't have the 700 but my HD650's needed a LOT of break-in time. Felt like forever because I don't use them often. They really opened up after a while and sounded nothing like when new. Senn makes some great headphones, the wait will be rewarding.
Possibly 200 hours of break in.
All of the Sennheiser 600+ series headphones are excellent performers. I have also found the 580s to be very good-sounding. And I was able to purchase 2 pairs right here on the 'Gon for less than $200 total.

Give those 700s a couple hundred hours and I think you'll be well-rewarded...

I have the 700s and it is taking a long time to break in. I think I am at 100+ hrs. I asked the Cardas rep at RMAF when they would have some cables for the 700s and he said they were working on it.

I will get new cables when they come out (if ever) and if there is not much improvement, I will be looking at another set higher-end cans.
Why worry. Just play it
I appreciate all the helpful responses. For now I'll listen to my 600s while a burn-in CD plays on the 700s. I don't recall the 600s needing this much break-in but the Cardas cable did. It's interesting that none of the reviews on 700s mentioned break-in. Surely they did not review them straight out of the box. If and when Cardas comes out with a cable it will likely be well over $300 - a third the price of the 'phones. One would think on a $1,000 headphone a great cable would be standard. Oh well I won't judge too soon. I'll let the break-in run its course and post my findings.
Well after about 150 hours they do sound better but I'm just not sure it's the headphone for me (I've also tried and sold the AKG's). It's quite different than the 600s. Physically they're great - light and comfortable. But sonically I think I prefer the 600s. Certainly that could change after more break-in time and a different cable. I'm sure Cardas will have a cable out soon and I'm sure it will make a big difference. But I think for now I will just be content with the 600s a while longer.
If you listen, say, an hour a day thru phones, you can let us know NEXT Christmas how those babies really sound.
Why don't you guys just play it and leave it playing for 10 days? You'll be 240h into break in at that point..