Wind vs high altitude cruise Yesterday I flew back from Tokyo down south against great head wind around 150kt at 34000’, the original flight plan was to cruise at FL240 for a while then climb up, but the captain decided to get up early, which resulted in a longer cruising time. 

It became a bit confusing to me in this case, 
One, The higher you go the stronger the winds, at the same time the fuel consumption is more efficient, but at what point do you say the wind factors wins over the fuel factors, ex. Take us longer to get to the destination resulting in more fuel burn. 

And what are some rule of thumbs to help me develop a decison wether to cruise high or low in terms of fuel saving. 

I found a wind altitude trade off in my A321 FCOM, but not too sure if the chart fits my situation, and I’m almost sure the captain didn’t take out the chart to form his decision. 

Thank you for your answers on advances. Any input is appreciated. 
Best regards,
Simply a matter of fuel burn rate per time in air.  Generally you want to go as fast and as high as practically possible against the wind. (Indicated Airspeed - headwind) x Altitude factor = groundspeed (temperature, atmospheric pressure, humidity may be factored in too)

Trip Time hours = Trip Distance miles/Ground Speed miles/hour

Fuel consumption = Trip Time hours x gallons/hour fuel burn rate at given power setting 

The pilot may have thought the headwind would be just as bad at FL 240 as at FL 340.
Weather prediction is not perfect, but apparently they did take enough fuel along to make it.

I would give them credit for that.