Haven't used PL Premium but, if it is freeze/thaw stable like most polyurethane sealants/adhesives, the freezer is your friend. Seal it in one of the ways mentioned above (or vacuum sealer if you want to go all-out) and put it in the freezer - understanding wife required. I've kept 3M 5200, Sika 291 & 292, etc. for more than a year in some cases. Only problem I have is remembering to get it out well before needed to let it come to room temperature. Some folks may get excited about chemicals in the food freezer but well sealed in plastic I don't see much risk - or use it as an excuse to get a dedicated shop (beer) fridge. YMMV
Steve