PVC Pipe Solvent/Cement, How do you Prolong in storage ?

Maybe refrigeration but that is just a guess. The material is probably self polymerizing. And to slow that reaction down reducing the temp may help. The chemistry rule of thumb is that reducing the temp by 10 deg (C) will reduce reaction rate by a factor of two.

Of course that brings up the question of do you want to keep a can of cement in your fridge. Would not bother me, I also store super glue - cyanoacrylate glue in my fridge.