Softener isn't labeled with an expiration date but it has a shelf-life through which it deteriorates, typically thickening. Some may separate into thinner and thicker component layers. Adding hot water to the measured dose as phillymatt53 suggests is helpful but of course increases the volume which, depending how much is used, may not fit into an automatic dispenser without overflowing it. Adding water to the bottle will thin it but also dilutes the product which may then call for a larger dose to get the desired effect.
I use softener only on specific loads, usually sheets/bedding, so a bottle lasts for many months. I have in a couple instances bought too large of a bottle which deteriorated so badly as to be unusable. Downey seems the worst. Snuggle is better in my experience. I recently bought a bottle of a TX-based grocery chain's softener, which is noticeably thin so better than Snuggle on the thickening point.