It's funny, I was actually just talking about this with a friend last week, and I hadn't noticed this thread until now.
I'm pretty flexible with my "use by" dates on food and go more based on smell/consistency/simi lar indicators, but (slightly off-topic, but this is why we were talking about it) I would /never/ take the risk of using an expired condom, and I don't even know what happens to them that would make them 'expire.' If it's the lube that means that they have to be marked with an expiration date, then I would probably care a lot less, for example.
I'd probably use lube packets based on smell/consistency/etc as well, but I have no idea if there's a reason it might be unsafe to do so, so I don't want to recommend it. I mean, things like vinegar and soy sauce have expiration dates on them, and I can tell you that from a microbiological standpoint, there is verrrrry little reason to respect that as long as you're not like, contaminating your source. Meaning that the single-serving packets that you get at restaurants (or single-serving lube samples) would be pretty safe by my assumption. Though you know what they say about assumptions.
OH - if they're oil-based lubes, though, I wouldn't use them. Oil can go rancid even just sitting there all sealed up. But water- or silicone-based lubes are safe bet imo.
I'm interested to hear if anyone knows for sure. Google isn't yielding anything that I'd consider to be an authoritative enough source (like a lube website, haha). But I mean, expiration dates help move product, so I can see why they wouldn't have info like that on their site. Or like, if a company said that it was safe and then someone used an old lubricant and had a reaction, they could probably try to say it came from the age of the product and kick up some shit. Doubly not worth it for the company.