It also depends on the ziplock baggies.
if this bags were stored in a shelf that had a bunch of old garbage or something really potent, its gonna taste like that in the bag which will make the shisha taste the same...
Also as Hajo said, depends on the setup. I've had shisha that has sat out for a month or two ( GO AF GRAPE) & it tasted wonderful & still the same 'buzz' i would have gotten if I got buzzes anymore & the same big clouds & taste.
BUT - Go Nakhla & sorry to hear it wasn't the same