OP
i suggested the antidessicant
becauise it seems your freezer/fridge
is not dry ( "frosty" ? ) not because you are storing it wrong.
moisture isn't good (for anything .. )
the folks at your store are probably correct,
unless where you are storing it is excessively hot,
or your temperature fluctuates wildly from freezing to boiling.
i've shelf stored most of my film for 15 years ( and some of it 2x that )
it's just fine ( high iso & low iso, b/w ). from my experience exposing/processing it ..
it is fine ... if you dig around there is a thread where someone who managed
the lab at a national portrait chain ( i think i got it right ) and how he and his workmates experimented with their film
by putting it in a "hot box" for a length of time to see how the film held up to excesses ..
( they were worried about excessive heat during transport from studio to lab )
the films were robust and were fine ... so, your photo shop guys weren't too far off,
but, if you ( like a lot of people ) are saving the film for making photographs at the end of days ..
the film will be the least of your worries
good luck with your fridge/freezer