Star San seems to me to get stickier and stickier with time. I mix it with distilled or RO water, keep it closed up, and keep it for a long time, and it stays clear, pH remains unchanged, and (so we are assured) effectiveness remains unchanged. But the stickiness, and I think aroma, increase. I assume it's something to do with the surfactant carriers. Like Denny, I just rinse it off.