Freezing and thawing cannabis seeds repeatedly will significantly lower your their viability rates. Each time you bring your seeds out of the freezer, moisture from inside condensates through the shell of the seed and evaporates. When this is repeated multiple times the process will eventually dry out and kill your seeds.
Another issue is mold. Every time your seeds are wet on the outside from thawing condensation you will greatly increase the risk for mold if and when you do decide to germinate. We do not generally advise freezing seeds to preserve them at all and certainly if you plan to remove them and restore them several times.
Even if you do not unthaw your seeds from frozen storage it is not inadvisable to remove seeds from the frozen environment, open the container of seeds to remove a number of seeds out and then refreeze the rest immediately. Simply by opening the container you will allow new moisture filled air into it and this moisture can subsequently damage your seeds by causing mold problems, amongst other issues, later on.