Honestly, I don't own a pair of true pac boots but have been looking much more intently at them recently for several reasons I'll explain below.
I went to college in the mountains of NC and basically lived in bean boots, as did most other folks I knew. These were perfect for the frequent rain that we got but really fell short once that rain turned to snow. The bean boots were excessively slippery on snow and ice and I personally found the thinsulate in the bean boots to be insufficient for any inactivity. The warmth was fine for walking to class but I couldn't use them for treestand hunting without freezing my feat within an hour or so being on stand. I still have those boots but they very rarely come out of the closet since then.
I did my first western elk hunt this year, DIY first rifle in Colorado. The temperatures turned frigid quickly and we got ~8 inches of fresh snow two nights before the season started. Given this was an early October hunt, I had planned (and did) to wear my uninsulated leather hiking boots. After days of slogging through snow which eventually turned to slush as temperatures warmed, the leather in my boots started to absorb water which would then freeze overnight. Mornings were frustrating because we had to wake up early to thaw boots by the fire before we could get them laced up and cold toes were a given every day. While I never got frostbite, I definitely lost some feeling in a couple toes which has still not totally come back.
I should mention that I normally run pretty warm but have poor circulation in my hands and feet so I typically have issues with both getting very cold. When duck hunting, I typically run 1600 gram thinsulate waders and rarely have issues with my feet overheating.
After my elk hunt, I started inventorying my gear and making a list of what I would do differently next year. Boots were the number one on my list. This trip made me realize that the idea of only having one pair of mountain hunting boots is a poor decision. I looked into insulated hiking boots a bit but after starting to read in more detail about pac boots, I realized this may be the solution I'm looking for. I love the idea of having a rubber base to keep my feet totally dry and a removable liner that I could throw in my sleeping bag at night to dry out and avoid the frozen boot issue. While I'd likely still wear gaiters with my pacs, I like the concept of being able to lace them up high to keep snow and dirt out, similar to the bean boots I used in college.
So to answer the question at hand, while I can't say when I "do" wear my pacs, I can certainly answer when I "will" use my pacs when I inevitably get a pair. First and foremost, as I described above, these would at least travel with me out west for any hunt after September. If the weather looks warm, they might stay in the truck but if snow and temperatures below 20 are in the forecast (like we experienced this year), I think the pacs will get the nod. If lows are expected near 0 (again like we experienced this year), the pacs will DEFINITELY get the nod.
While western hunting was what sparked my initial interest in the pacs, I actually see a lot of value in them for eastern hunting as well. As I mentioned, my feet get really cold but when hunting public land out here I'm usually hiking at least a half mile if not further with my treestand on my back to get away from the crowds. This leaves me in a predicament because my insulated rubber boots are HORRIBLE for hiking but my feet freeze in my uninsulated hiking boots while sitting in the stand. I think a pair of pacs will bridge that gap nicely from late october through december for eastern treestand hunting.
I think this is a really cool giveaway that you're doing and obviously would love to win (and would be happy to report back on how my experience with the pacs lined up with my expected use), but regardless I hope the above is helpful