I dry hop with ~3 days left in fermentation while still active (55°F for Lagers, 65°F for Ales).
I realize it bucks the ‘dry hop cool’ research. But I have ulterior motives.
I want the yeast to consume, and the CO2 produced to push out, any O2 I introduce when I open the fermenter. That’s the theory anyway…
*Disclaimer*: Any comment I add is simply the way I brew beer. I am not paid or sponsored by anyone. There are certainly other ways that can be equally effective which other brewers may contribute. This is what I’ve found that works for me using my equipment and processes so I offer this for your consideration. YMMV