  The free decay of MHD turbulence at large Reynolds numbers is studied
numerically using a shell model. We study the statistical properties based on
representative sample of realisations (128 realisations for each type of
initial conditions) over the period of $10^5$ large-scale turnover times. The
performed simulations show that the force-free non-helical MHD turbulence can
demonstrate two different scenarios of evolution in spite of similar initial
conditions. Within the first scenario, the cross-helicity accumulation is so
fast that the energy cascade vanishes before significant magnetic energy
dissipates. Then the system approaches the state of maximal cross-helicity.
Within the second scenario, the cascade process continues to remain active
until time $10^4$ in units of large-scale turnover time. Then the magnetic
field becomes vastly helical due to magnetic helicity conservation. Thus the
magnetic energy does not dissipate with kinetic energy.
