I am wondering how do I compare two futures of different lengths. Let's say I am to need to buy a future for a year and I can buy two kinds of futures, one for half a year which is x higher than the spot price and another for a quarter which is y higher than the spot price. I need to choose which is better for me (for simplicity we can assume in half a year I will have the other asset, so I care only on cost over spot and such things at the moment of the purchase).
Just comparing the per quarter gain\loss I will have from each of the futures for a quarter may not be enough, as I don't know what will be the premium of the new quarterly future following (or do I? do I have an expectation?). Is there something optimal to do? (e.g. buy the best one in terms of a quarter and do something sophisticated when the new quarterly is created?)
Thank you very much!