I can see where you’re coming from. Admittedly, many people believe (myself, once) that things that are stable, non-harmful, and non-toxic, can be used for as long as they last. Indeed, Glycerin is a stable compound. The toxicants that enter usually die from osmosis water loss.
But I think, along with many experts, anything that’s beyond the expiry date, should NEVER be used regardless of how safe it looks and what purpose it has. There’s a reason why it has an expiry date in the first place, right?
So I would suggest, throwing away the glycerin if it’s outdated. It might be non-toxic still, but it might not be healthy either.