life of a single free neutron is nearly 15 min. what is the life if 2 are more neutrons adhering together? will it increase or same?
Well, I don't understand the maths, but the neutrons in a neutron star are prevented from collapsing indefinitely by what is called degeneracy pressure. This results from the Pauli exclusion principle - neutrons are fermions so no two can exist in the same state. The same condition applies to the protons and electrons they would have to decay into, and it must turn out that those states would have higher energy.
Actually, thinking about this now prompts a question in my mind: are neutron stars composed solely of neutrons, or are there still a limited number of proton and electron states available, with the numbers in each state determined by the respective energy levels?