Not sure if you're talking about "checking in" or reprinting a BP, but I can tell you with 100% certainty that kiosks at my regular WN airports reprint BPs well past the T-1 hour mark. In fact, just last week, I printed one in TUS at T-20 minutes.

I've routinely print BPs at the unmanned PHX stations by security at T-30 minutes, and at LAS and LAX at T-20 minutes. Heck, I did one at T-10 minutes in OAK.

Again, I'm checked in with A-list status, but I've never had any trouble reprinting BPs that close to departure.