phr129,
I believe that polyquat 60 should remain in good condition for a while. Store it in a cool location out of the sun. Heat and sunlight are what degrade most pools chemicals, sometimes slowly, somtimes (as with chlorine), fast.

cynlys,
polyquat 60 is the recommeneded algaecide. It is not a brand name but the common name of the active ingredient. Look on the label for poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride] and check out this page on PoolSolutions for more info:
http://www.poolsolutions.com/gd/polyquat.html

Also, HTH is no longer selling polyquat so you will not find the product that is illustrated in the picture on that page!