What's the time limit for a Council's sessions to reconvene after a suspension? If a Council's sessions are suspended, such as was done at the Vatican Council by Pope Pius IX, due to the Roman heat, but the sessions could not be reconvened due to the attack on Rome and the Vatican in 1870, is there a time limit for the Council to be reconvened?  Pius XII was planning to reopen the Council and had preparations made for new sessions, but he was unable to follow through due to lack of cooperation (according to some sources).
There is no time limit. Convening of general or ecumenical councils is entirely up to a pope. Their purpose is to advise a pope, and they authoritatively teach only what the pope ratifies.

Fr. Hardon defines them as:


  Authorized gatherings of bishops for the purpose of discussing ecclesiastical problems with a view to passing decrees on matters under discussion. In Roman Catholic terminology, if all the bishops are called to participate and actually represent the Christian world, the assembly is called ecumenical, which means universal; if only part of the hierarchy is invited, the council is particular. The latter may be plenary or provincial, depending on whether a single provincial area, e.g., the dioceses of Ohio, or a whole country sponsors the gathering. Church councils, even on a provincial basis, enjoy juridical authority in religious questions that is distinct from the legislative powers of individual bishops. In this respect also, councils differ from episcopal conferences, which are not, as such, legislative assemblies.