That 8 oz. package (try Amazon or eBay in your home country) should get you 3 tire changes or one application every 10,000 miles, uhhhh, I mean every 16093.44 kms, whichever comes first, Mike. If it's stored properly, as airtight as possible, I wouldn't be overly concerned with the expiration date.
No apologies warranted, mate, as lubing one's splines is an essential servicing that could cost one very dearly if not done at proper intervals!