I had an problem with these little fuckers in my last place, and the exterminators have a difficult time killing these little bastards. I've never been bitten (knock wood) but a bite from one is most likely what killed my cat and possibly a small caged animal my son was keeping, according to the vet.
I don't know if the winter would have a great deal to do with it, but I can see where it might - but they are typically most active mating and laying eggs in May through August in our area, and a recluse spider in the outdoors that may have died due to cold weather would still be one that would most likely die anyway given the life-cycle of the spider, as juvenile spiders can survive some pretty cold temperatures where older ones cannot, and they are a species entrenched in man-made structures. All of the exterminators I called (and I tried three) told me that in most areas of Kansas City (with very few exceptions), if you are in a wood framed house or similar sized structure (given the KC area average 2000 sq. foot home), they can safely estimate that if the structure is untreated and more than a year old, that there are 75-100 of them right there along with you. It's fraking scary, they are everywhere (you might live your entire life in the home and never see one, but they are there), and they are harder than an ex-wife to kill (something I grew up hearing occasionally, while my father was being bled for alimony). When they told me there might be as many as 500 in my last place (40 year old wood framed home), I looked for new construction and had it pretreated before I moved in.