(Energy stock, oil services story updated for Thursday market close)NEW YORK ( TheStreet) -- Energy stocks were again leading the Street on Thursday and new 52-week highs for some stocks in the sector continued to be the rule -- and, in particular, for the oil service sector stocks. Whether it's Halliburton ( HAL), Baker Hughes ( BHI) , Schlumberger ( SLB) or Weatherford International ( WFT), oil service stocks are sitting at or near 52-week high levels attained this week; all four companies hit new intraday 52-week highs on Thursday, before ending the day slightly lower. Between rising crude oil prices, recent road-showing from the oil service companies (including last week's Credit Suisse energy conference), a U.S. drilling market that continues to defy reports of a peak being reach, and the continued unrest in the Middle East, oil service stocks have been a big part of the equities rally in 2011, doubling the returns of the S&P 500 year-to-date. It's all the energy stocks moving up, though -- among the integrated oil majors ConocoPhillips ( COP) hit a new intra-day high on Thursday. Yet the oil service stocks make a good group from which to consider if energy stocks are vulnerable to a pullback. David Havens, analyst at Sterne Agee, notes that the PHLX Oil Service Sector Index has not had one pullback since September -- after a five-year period during which pullbacks have been typical -- therefore, the OSX chart suggests that a pullback from current levels would not be surprising. Indeed, it all raises the question: Are the oil service stocks priced for perfection at this point -- meaning any signs of weakness and they sell off -- or is there yet another economically justified, and sector fundamentals-supported, leg up in these stocks in 2011? Alan Laws, analyst at BMO Capital Markets, argues that oil service stocks are not "priced for perfection" and that there is still earnings growth left in these stocks. The BMO analyst admits that "it's not a stoic group of stocks," so there is always risk of a pullback, especially given the surge, but he is more inclined to see potential for sideways trading, a pause as opposed to a leg down, awaiting a raised Street outlook for 2012 that won't come until the mid-year 2011 point. There are several ways to look at this question. What follows are some of the key points for investors to consider.