I've lost coil twice. Once was during driving. I lost a single cylinder, check engine light turned on. I was able to drive up to 70Km/h without my check engine light start blinking (means "you can melt your catalytic convertor, exhaust is too fuel rich, reduce throttle!").
Went to my service guy, he put down his tea on my engine, replaced it and his tea was half (~10 minutes). Also put in a new set of plug wires since my set was ~18 years old and gone hard at that point.
I went to office, lost 30-40 minutes at most.
The second one happened when the car was at park, at night. Started it in the morning, it was running off, so went to service. Same story. 70Km/h speed, 10 minute change, sans the cables this time.
Newer cars tend to use one per plug. It's just a disconnect, pop-off, push in, plug, go. 2-3 minutes at most.