Too late to brumate?

[FLUGATRON]

My California Kingsnake is around 3 years old and has been refusing food since mid September, I’m wondering if it’s too late to start the brumation process or not. Last year he went off feed around this time for about 2 months but wasn’t brumated. He’s acting normal and looking healthy, just ignoring food.
Should I try to brumate him? What’s the best way to go about that?
Any help is appreciated,
Thanks.