If you make a starter for the yeast the day (if you use a stir plate) or two (if you don't) before your brew day, you'll KNOW the yeast is ready to get to work. Since I've been making starters on a stir plate, I have active fermentation sign within 6-12 hours, with full activity in under 24.
I get my yeast locally ONLY... Not to knock getting it shipped to you, but at least I have someone I can get in front of, with a pack that doesn't swell (if I ever get one) and get a replacement right there. I just used a pack from mid July this past Saturday, with a starter (made Friday evening) and the pack swelled up before I pitched it into the starter (within a couple of hours of smacking it, and confirming the nutrient pack was popped).
You should be able to keep the Wyeast packs viable, in your fridge, for six months (maybe longer). So, maybe order up several during the cooler months (but not cold enough to freeze them in transit) and stockpile them. I still have two packs in the fridge, one of them is the 1882-PC strain. I plan on using it in my next batch and expect to have zero issue with doing so. I might make my starter a bit earlier than usual, but probably not.
Another item that could be giving the yeast a serious leg up... Oxygenate with pure O2... Check out the threads about doing so...