For a completely new domain, I’d say I started seeing the first consistent organic traffic around the 4–6 month mark. Before that, there were mostly impressions and occasional clicks from long-tail queries.
The bigger jump came around months 6–9, when several posts started ranking at the same time. I think the niche and keyword difficulty make a huge difference though—low-competition topics can move much faster than competitive ones.
I’d track clicks and ranking positions rather than just impressions, since impressions can increase for months without producing much actual traffic.