In this paper, the factors of affecting thermal fixing efficiency, and lifetimes of fixed gratings under both illumination and dark conditions are analyzed theoretically. The characteristics of fixed reflection gratings in Fe:LiNbO3 and Ce:Fe:LiNbO3 crystals recorded using red wavelength have been extensively studied. The experimental results show that development of ionic gratings in crystals with high concentration and deep reduction is not available. For lightly doped unreduced crystals, the thermal fixing efficiency up to 50% has been achieved. The lifetime of the ionic grating under continuous illumination is up to 300 hours, which is one hundred times more than that of the electronic grating. The dark storage time can reach 4 months, ten times more than the lifetime of the electronic grating. The experimental results demonstrate that the conditions required for increasing thermal-fixing efficiency will decrease the lifetime of ionic gratings, as predicted by theory.