Shake the bottle. If it wiggles around like water, you should be ok. But if it clings to the bottle at all, like a light oil, you can still use it for building, but I wouldn't trust it for hinges.

Think about this:

The CA MUST wick into the hinge fibers and into the balsa fibers. Picture dripping 4 or 5 drops of water on a napkin. The water will wick its way out from where you dripped it. But if you dripped pancake syrup instead of water, it may wick a little, but nearly as much.

It's worth the price of a bottle of new Thin CA to be safe.