Easily managed can go to 'ah, bugger' quite quickly in busy airspace!
Only if fuel is expensive... Extra flight time costs money as well
Yep, the appropriate cost index should vary between airlines, aircraft types and even routes. Here in Europe, fuel is a high cost, so the CI is often low. In my airline, salary and maintenance costs are tightly controlled, hence they're less important than fuel. Moreover, there's little emphasis on scheduled arrival times in my company, so they'd rather we stuck to the most fuel efficient flight profile.