Deep-freezing of bacterial DNA for thermal denaturation and hybridization experiments

What effect freezing purified DNA at −70 C and then keeping it at −21 C for several months might have on the thermal denaturation and hybridization was investigated. One part of each DNA sample was stored at 4 C, and the other frozen at −70 C and stored at −21 C, and the results of thermal denaturation and hybridization experiments were compared. They show that freezing at −70 C and then storing at −21 C for half a year or probably even one year do not significantly affect thermal denaturation and hybridization.