How early should I buy tickets for 7 from NY or Philly to Rome in February? I'm hearing 4-5 months. Sound good?

There is nothing magical about when to buy. Could be six months, four months, two months. Watch the price for awhile to determine range and buy when it hits a reasonable fare. The probability of buying at the lowest fare is low so just shoot for a reasonable to low fare.

I agree. There's no set amount of time in advance that guarantees you the best prices.

USAir has DIRECT flight PHL to FCO, you should be able to get it for 870+/- , keep on checking, use "low fare finder" option on web site. but i have found best fares usually around 60-90 days out. but if you see the fare for around this price, that is lowest i have seen, IMO book it.

Check skyscanner.net and farecompare.com, amongst others, and when you get a fare that sounds reasonable, book and forget about it!

You are looking for a round-trip fare and not a multi-city fare, right?

Sign up for fare alerts from 'kayak' and 'yapta'. I read several articles that indicate 3 months out the prices get better. Closer than 6 weeks and you probably wont find the best deal.
Best deals are posted on the travel site Tues afternoons.
Cheapest days to travel are Tues, Wed and Sat. I've been watching fares Atlanta to Rome for several weeks and I think I'm seeing the best prices now for mid Oct.

Thanks all - I've been "alerted" by Kayak every morning for a good few weeks now. Not a big fan of farecompare but I'm going to try skyscanner.
Thanks for all the input. We're down to a great flight on aer lingus that leaves jfk / nyc and makes a quick stop in dublin. it's at $704 - pretty fine!

I would not jump until Jan.
Feb should be lowest of the year.