The bitter contract dispute between the city and the firefighters’ union could last much longer than the year deadline that City Council members hope. Syracuse attorney Nathaniel Lambright, who is representing the Watertown Professional Fire Fighters Association Local 191, warned on Tuesday that the labor dispute may not be resolved for another two to 2½ years while it continues through the lengthy appeal process. He made that assessment after a state Supreme Court judge reserved decision on Tuesday on the city’s motion for a stay of arbitration over the “minimum manning” clause, which requires 15 firefighters must be on duty at all times. It’s been the main sticking point during the 3½-year contract stalemate.