How frequently, and in which situations do you use quantitative EEG for the detection and/or monitoring of delayed cerebral ischemia after aneurysmal SAH?

Almost never.

I have heard of using EEG to monitor for delayed cerebral ischemia (alpha/delta ratio) but never have seen it in practice (working for the last 5 years or so).

TCDs are more commonly used to monitor for vasospasm.

Not at all. I'm not aware of any evidence for this.

I’ve only seen it in fellowship and haven’t seen it being used anywhere post-training.