B727 CLBING TO FL270. FLC BUSY STUDYING THEIR APCH PLATES AND FORGETTING THE EXTRAORDINARY PERFORMANCE OF THE LIGHT ACFT ON A COLD DAY ALLOWED THE ACFT TO CLB TO FL279 BEFORE CORRECTING.

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ON A SHORT FLT FROM ALB TO PWM WE HAD AN ALTDEV OF APPROX 1000 FT. WE WERE IN OUR 11TH HR OF A 12 HR CREW DUTY DAY AT APPROX XA20 PM. A VERY LIGHT ACFT LOAD COUPLED WITH EXTREMELY COLD TEMPS MADE ACFT PERFORMANCE MUCH BETTER THAN NORMAL. WE ESTIMATE THE ACFT WAS CLBING IN EXCESS OF 4000 FPM AT THE TIME OF THE DEV. OUR CLRNC FROM ZBW WAS TO CLB TO FL270. PASSING FL230 THE CAPT AND I BEGAN TO DISCUSS THE POSSIBILITY OF TWR CLOSURE OPS AT PWM WHILE STUDYING OUR APCH PLATES. CLBING THROUGH FL270 THE ALT CHIME REMINDER SOUNDED (NORMALLY SOUNDS 500 FT ABOVE/BELOW SETTING) AND THE CAPT IMMEDIATELY DISENGAGED THE AUTOPLT WHILE MANUALLY PUSHING FORWARD ON THE YOKE. WE CONTINUED TO CLB TO APPROX FL279 BEFORE DSNDING BACK TO OUR FLT LEVEL OF FL270. ZBW MADE NO MENTION OF OUR ALTDEV AND A QUICK SCAN OF THE TCASII INDICATED NO CONFLICTING ACFT WITHIN 25 MI. BASICALLY; OUR CREW COORD BROKE DOWN BY NEGLECTING THE 1 AXIOM PLTS LEARN FROM THE BEGINNING OF THEIR FLYING CAREERS TO NEVER DISREGARD. THAT IS 'SOMEONE NEEDS TO CONSTANTLY FLY THE ACFT.' WE BOTH BECAME OCCUPIED STUDYING OUR APCH PLATES AND LET THE ACFT PASS THROUGH OUR ALT CLRNC. CONTRIBUTING FACTORS WERE THE BETTER THAN NORMAL ACFT PERFORMANCE AND THE LATER HR OF THE DAY; IN A LONG CREW DUTY PERIOD.