Well it's only been a week since I did it, and I've only been out in the rain once or twice, but the new-ish chain still looks near enough new.
When I put it on my motorbike, I rode from November through the whole of the last crappy winter to March, and only reapplied it twice or maybe three times during the winter. I had some surface rust after the really snowy week, but that came off with a wire brush and a wipe and things were fine again.
Motorbike chains take a real hammering compared to pushbikes, I think it's probably better than you actually need. I'll probably get a new can when I finish this one, it's about £8 from Halfords and should last a good 6 months to a year. And it comes with a cool straw adapter