CAN they go bad? Yes.
If they're stored improperly (especially in heat), and/or allowed to age for a VERY long time (ie years), then yes, germination rates will be affected.
The longer and worse they're stored, the fewer seeds will germinate.
I've personally seen seeds germinate after 15 years of storage, and heard of multiple cases of seeds being germinated after MUCH longer periods than that.
SHOULD they go bad? No.
Not in only a matter of a few months, so long as you keep them cool and dry.
As mentioned, under NORMAL conditions, cannabis seeds are supposed to last through the winter before germinating in the spring.
You can also bet that most of the seeds you'd be obtaining from a seedbank have been sitting in that bank for at least a few months before they were shipped out to you.