about three or so weeks ago and I've been riding on them since ( https://www.biketiresdirect.com/product/schwalbe-marathon-winter-plus-700c-tire-hs-396?sg=500 ). I plan to ride them snow or no snow for the duration of the winter since I don't want to go through the whole trouble of taking them off and putting them on only when there's snow on the ground. The studs are audibly present whenever I ride and it took a while to get used to the added resistance, but it's all good now. The studs give me some added confidence for any riding that involves snow/ice on the pavement.

I just hope I don't wear the studs down too much during my non-snow riding days this summer. I suppose time will tell in that regard.