Just out of curiosity?

2012

Christmas 2014.

September 2015. I think mid summer 2014 to late summer 2015 was the ideal time to buy. Good games came out in those years and you had a backlog. Buying at launch means dealing with droughts, buying after that doesn't make sense with the Switch coming. I mean despite droughts, I have no lack of games I would buy if I had the money. Hyrule Warriors, Yoshi's Wooly World, New Super Mario Bros U, Donkey Kong Country Tropical Freeze, Nintendo Land, Mario Maker, all games I still have interest in purchasing but haven't yet.

Bought mine earlier this year for a steal. Target Australia were doing a clearance on the Mario Maker Wii U bundle(with physical game and amiibo). Got it for $299AUS($220US) and do not regret it. Perfect companion to the PS4 as the games are vastly different.

Late 2013 or early 2014, don't remember exactly -.-

At teh launch

Bought it used this past year. Got it for Mario Kart, but then I unexpectedly had SM3DW on the hard drive. Then I got Xenogears and all things considered, I dumped so many hours into this machine I feel like those three games were worth the price I paid (maybe $180 CAD)

At launch.

Won't be making that mistake again, with any console

2013. For the time being, not buying any Nintendo console again.