I have spools of braid that I have kept in the house for 4 years with no loss of quality. I keep a roll or two on the boat for up to two years and haven't noticed any loss of quality. On my reels, I switch it out every year at start of season.
Capt. Craig Copeland
2013 Nautic Star 2110 Shallow Bay Boat
Nautic Star Boats Pro Staff (nauticstarboats.com)
Redneck Fish'n Jigs Pro Staff (redneckfishn.com)