Ah... I googled "81mg aspirin" and see that these are being billed as "low dose" ... the sort of thing you take every day to ward off all sorts of ailments based on all sorts of dubious medical studies.
Might have to go back and get the real shit.
First, you have to pay close attention to what you buy...the 81mb tabs are much more prevalent than the "full sized" 325mg tabs.
Why? Aspirin has many properties, as do most meds, one of which is it increases clot time...in simple terms, it makes the platelets less "sticky" and less prone to clump or clot. The benefit is it makes it harder to form a clot within an artery/vein, thereby decreasing the chance of a clot forming and blocking off one of the small arteries that feed the heart or brain. Clot formation within the vasculature of the body is especially prevalent in the most distal vessels, such as the veins in the feet/legs, where the blood flow is the slowest.
That's why someone presenting to the ER or wherever with chest pain will be given an aspirin immediately...it's been shown to actually work darned well in "slowing down" a heart attack caused by a clot.
The downside is also from it increasing clot time, which means it'll take a bit longer to stop bleeding from a cut, for instance. Not hugely, but it's there.
Another thing aspirin does better than tylenol or advil (ibuprofen) is reduce swelling. Much more effective than either of those.
Of course, aspirin has its downsides/side effects. It is to never be given to young children due to it causing Reye's Syndrome. This is why the proliferation of chewable orange flavored children's aspirin has largely disappeared.
The second is the caustic nature of aspirin on mucus membranes which can cause esphageal/gastric upset/erosion. This is easily mitigated/eliminated by buying only enteric coated aspirin (almost all aspirin is coated these days, btw) and by ensuring you drink more than one small swallow of water when taking the aspirin.
As for the expiry date...true, some expiry dates on meds are "ultra conservative", although there are some meds that do have definite expiry dates. Aspirin isn't one of those, though. My rule of thumb is aspirin is "gone" by its smell. Aspiring typically has very little odor. If you sniff the aspirin and get a shapr, almost vinegary smell, it's going bad....esp. if the aspirin is changing color (I've seen yellowish colors on very old aspirin.) Otherwise, it's probably good.
Aspirin is an excellent med...and damned near as good as the newer NSAIDS out there, esp. in relation to swelling reduction and reducing clot formation.