My nail polish collection is large. Polishes kept in good condition (away from heat or light) can last a long time, longer than the two years many people quote. A good thinner (I use Seche Vite) can also revive them. I have tossed polishes when thinner cannot save them or they have obviously gone bad, but it is rare. When I started collecting polishes again, I tossed all polishes older than the summer of 2013. To avoid ordering duplicates, I created a spreadsheet. Swatching them with these spoons I purchased from Amazon will help me compare the colors, finishes, and overall quality. All polishes only have one coat, because I wanted to spot the difference between my sheer and opaque polishes. We’ve all seen polishes that look dark in the bottle only to need 3-4 coats for opaqueness. No polishes have base or top coats either, because that can change the way the polish looks.