Of course you will have to make this calculation on the fly, but sometimes I find myself facing an particular army build- in this case IG template spam where phase out becomes a real worry despite my tricks. When this happens by going second I don’t have to worry about phase out by the end of the game. PO is calculated at the start of the Necron turn so by turn five, if I dip below phase out, yet the game ends- by going second I potentially win by not phasing out due to the end of the game. Sometimes that means I have to go for the turn five win, but with cover, monolith blocking, etc. one can definitely last five turns against more armies.